IB Physics SL- Unit 4 Test: Electric Fields and Currents 1.
The diagram below below shows the electric field field lines in a region of space. space. A positively charged particle moves from P to Q.
Which of the following is correct?
Change in potential energy of particle
Change in potential between P and Q
A.
decreases
zero
B.
decreases
negative
C.
increases
zero
D.
increases
negative (1)
2.
In the circuit shown below, the cell has negligible internal resistance. resistance.
Which of the following equations is correct? A.
I1 = 2I2
B.
I1 = 2I3
C.
I2 = 2I3
D.
I3 = 2I1
3. In the circuit below, the the voltmeter has a resistance 100 k Ω. The battery has negligible internal resistance and emf 6 V.
The reading on the voltmeter is A.
0 V.
B.
2 V.
C.
3 V.
D.
4 V. (1)
4.
Which graph best represents the relationship between the current I and the voltage V of a filament lamp.
(1)
(1)
5.
Which of the following is a unit for electrical resistance? resistance? (use P=iV or i^2R or V^2/R . . . Hint) –2
B.
AV
–2
D.
WV
A.
WA
C.
VW s
–1
–2
3. In the circuit below, the the voltmeter has a resistance 100 k Ω. The battery has negligible internal resistance and emf 6 V.
The reading on the voltmeter is A.
0 V.
B.
2 V.
C.
3 V.
D.
4 V. (1)
4.
Which graph best represents the relationship between the current I and the voltage V of a filament lamp.
(1)
(1)
5.
Which of the following is a unit for electrical resistance? resistance? (use P=iV or i^2R or V^2/R . . . Hint) –2
B.
AV
–2
D.
WV
A.
WA
C.
VW s
–1
–2
6.
An isolated charged metal sphere has radius r. Which diagram best shows the variation with distance d from the centre of the sphere of the potential V?
(1)
7.
Three resistors P, Q and R, are each labelled 100 Ω. They are connected as shown.
The total resistance, when measured between points X and Y, is found to be 200 Ω. What is the correct explanation for the resistance reading? A.
Resistor R is zero
B.
Resistor R is infinite
C.
Resistor P is zero
D.
Resistor P is infinite
8.
Which of the following is the correct value of the electronvolt, measured in SI Units? –19
N
B.
1.6 × 10
–31
N
D.
9.1 × 10
A.
1.6 × 10
C.
9.1 × 10
–19
J
–31
J (1)
9.
Two charged plastic balls are separated by a distance d in a vertical insulating tube, as shown.
The charge on each ball is doubled. Coulomb’s law applies to the force between the balls and friction with the walls of the tube is negligible. What is now the separation of the balls? A.
C.
2d
B.
d
D.
4d
10.
The graph below shows the variation with current I of the potential difference V across a filament lamp.
The resistance of the lamp when I = 1.5 mA is A.
950 Ω.
B.
400 Ω.
C.
0.95 Ω.
D.
0.40 Ω. (1)
11.
In the circuit below, resistors X, Y and Z are connected in series with a 9.0 V supply.
Resistors X and Z are fixed resistors of resistance 3000 be varied between zero and 3000 Ω.
Ω.
The resistance of resistor Y may
Which of the following gives the maximum range of potential difference V across the resistors X and Y?
12.
A.
0 to 6.0 V
B.
3.0 V to 6.0 V
C.
4.5 V to 6.0 V
D.
4.5 V to 9.0 V
The graphs below are the current-voltage ( I-V) characteristics of three electrical components P, Q and R.
Which component(s) has (have) constant resistance? A.
P only
B.
R only
C.
P and Q only
D.
P and R only (1)
13.
Two pairs of uncharged parallel plates are placed in a vacuum and are connected as shown.
A negative charge of magnitude q is placed on plate X. Plate Y is connected to earth. Which of the following diagrams shows the distribution of charge on the plates?
(1)
14.
X and Y are two identical conducting spheres separated by a distance d. X has a charge +6 μC and Y has a charge –2 μC. The electric force between them is + F ( ie attractive). The spheres are touched together and are then returned to their original separation d. The force between them now is A.
+F.
B.
C.
–F.
D.
(1)
15.
A conductor of constant resistance dissipates 6.0 W of power when the potential difference across it is 12 V. The power that will be dissipated in this conductor when the potential difference across it is 24 V is
16.
A.
6.0 W.
B.
12 W.
C.
24 W.
D.
48 W.
The resistors in each of the circuits shown below each have the same resistance.
Which of the following gives the circuits in order of increasing total resistance? A.
P
Q
S
B.
Q
P
S
C.
S
Q
P
D.
P
S
Q
17.
Which diagram below best represents the electric field pattern between a positively charged conducting sphere and an earthed metal plate?
(1)
18. Which of the following correctly describes the nature of electric potential and electric field strength?
Potential
Field strength
A.
Scalar
Scalar
B.
Scalar
Vector
C.
Vector
Scalar
D.
Vector
Vector
19.
The graph below shows the variation with potential difference V of the current I in an electrical component.
Which one of the following is a correct statement about the resistance of the component? A.
For potential differences greater than V0, the resistance is constant.
B.
For potential differences greater than V0, the resistance decreases with increasing potential difference.
C.
The variation of current with potential difference is linear and so Ohm’s law is obeyed.
D.
For potential differences less than V0, the resistance is zero. (1)
20.
A battery is connected to a r esistor as shown below.
The battery transfers energy EB when charge Q passes completely around the circuit and the resistor transfers energy ER. The emf of the battery is equal to A.
B.
C.
D.
(1)
21.
Three equal point charges X, Y and Z are fixed in the positions shown.
The distance between q1 and q2 and the distance between q2 and q3 is 1.0 m. The electric force between the charges at X and Y is F. The electric force between the charges at X and Z is A.
C.
B.
F.
D.
2F. (1)
22.
The diagram below shows a charged rod R suspended by insulating strings. When a stationary rod S is placed nearby, rod R is attracted towards it.
Consider the following statements regarding the possible nature of the rod S. I.
Rod S is charged
II.
III.
Rod S is an uncharged conductor.
Rod S is an uncharged insulator.
Which statement(s) can explain the attraction of rod R to rod S? A.
I only
B.
II only
C.
III only
D.
I and III only (1)
23.
In the circuit below the battery has emf 6.0 V and negligible internal resistance. The three resistors each have resistance 10 Ω. A high resistance voltmeter is connected as shown.
The reading of the voltmeter is A.
2.0 V.
B.
3.0 V.
C.
4.0 V.
D.
6.0 V. (1)
24.
An electrically neutral conducting sphere is suspended vertically from an insulating thread.
A point charge of magnitude Q is brought near the sphere. The electric force between the point charge and the sphere A.
depends on whether Q is positive or negative.
B.
is always zero.
C.
is always repulsive.
D.
is always attractive. (1)
25.
Which one of the following statements about electric potential gradient is correct? A.
Electric potential gradient is numerically equal to the gradient of the electric field.
B.
Electric potential gradient at a point is numerically equal to the electric field strength at that point.
C.
When one joule of work is done in moving one coulomb of charge between two points, the electric potential gradient between the points is one volt per metre.
D.
When one joule of work is done in moving one coulomb of charge to a point, the electric potential gradient at that point is one volt per metre. (1)
26.
In which one of the circuits below is it possible to vary the current in the lamp by adjusting the variable resistor? The cell has negligible internal resistance.
(1)
27.
Four point charges of equal magnitude Q are placed at the corners of a square as shown below. The centre of the square is at the origin of the x-axis and the y-axis.
At which position, or positions, is the electric potential due to the four point charges equal to zero? A.
At the centre of the square only
B.
Along the x-axis only.
C.
Along the y-axis only.
D.
Along the x-axis and the y-axis. (1)
28.
Two filament lamps X and Y are designed to operate at normal brightness when the potential difference across the lamps is 6 V. Each lamp will just light when the potential difference across it is 3 V. The two lamps are connected in parallel to a 4 V supply of negligible internal resistance as shown below.
The filament of lamp X breaks so that there is no current in it. The filament of lamp Y will A.
glow at normal brightness.
B.
glow at more than normal brightness.
C.
glow more dimly.
D.
stay at the same brightness.
29.
X and Y are two points in an electric field. The potentials at X and Y are VX and VY respectively where VX > VY. A small, positive test charge + q is placed at X. Which of the following is the work done per unit charge by the electric field on the charge as the charge moves from point X to point Y?
30.
A.
B.
C.
D.
A resistor of resistance 1.0 Ω is connected in series with a battery. The current in the circuit is 2.0 A. The resistor is now replaced by a resistor of resistance of 4.0 Ω. The current in this circuit is 1.0 A.
The best estimate for the internal resistance of the battery is
31.
A.
1.0 Ω.
B.
2.0 Ω.
C.
4.0 Ω.
D.
5.0 Ω.
Which of the following is a correct statement of Ohm’s law? A.
The resistance of a conductor is always constant.
B.
The current in a conductor is always proportional to the potential difference across the conductor.
C.
The resistance of a conductor increases with increasing temperature.
D.
The resistance of a conductor is constant only if the temperature of the conductor is constant. (1)
32.
An electron and a proton are accelerated from rest through potential differences of the same magnitude. After acceleration the speed of the electron is ve and the speed of the proton is vp. Which of the following is the best estimate for the ratio
A.
2000
B.
C.
D.
33.
The diagram below shows two long parallel plates that are oppositely charged. A positive test charge +q is placed along the dotted line XY.
The charge +q is moved from X to Y. Which one of the following best shows the variation with distance d from X of the magnitude F of the force on + q?
34.
In the two circuits X and Y below, each cell has an emf E and negligible internal resistance. Each resistor has a resistance R.
The power dissipated in circuit X is P. The best estimate for the power dissipated in circuit Y is
A.
C.
B.
2P.
D.
4P. (1)
35.
A heater has a resistance R when the potential difference across it is 12 V. In the circuit below, it is connected in series with a 36 V supply and a resistor S.
To ensure that the potential difference across the heater is 12 V, the resistance of the resistor S should be A.
.
C.
B.
.
.
D.
2R.
(1)
36.
The element of an electric heater has a resistance R when in operation. What is the resistance of a second heater that has a power output three times as large at the same operating voltage? A.
C.
B.
3R
D.
9R (1)
37.
A battery of emf E and negligible internal resistance is connected to three resistors, each of resistance R, a voltmeter and a switch, as shown below.
The voltmeter has infinite resistance. What are the readings on the voltmeter when the switch is open and when it is closed?
Switch open
Switch closed
A.
0
less than ½ E
B.
0
½E
C.
½E
less than ½ E
D.
½E
½E (1)
38.
39.
Electric field strength is defined as A.
the force exerted on a test charge.
B.
the force per unit positive charge.
C.
the force per unit charge. positive test charge.
D.
the force per unit charge exerted on a
A positively charged sphere falls vertically in a vacuum between two long parallel plates carrying opposite charges. Which one of the following diagrams best shows the path followed by the sphere?
40.
A plastic rod is rubbed with a cloth. At the end of the process, the rod is found to be positively charged and the cloth is found to be uncharged. This involves the movement of A.
positive charge from the cloth to the rod. cloth.
B.
positive charge from earth to the
C.
negative charge from the rod to earth. cloth.
D.
negative charge from earth to the (1)
41. A cell of emf E and internal resistance r is connected to a variable resistor. A voltmeter is connected so as to measure the potential difference across the terminals of the cell. Which one of the following is the correct circuit diagram of the arrangement?
42.
(1) A proton and an alpha particle are accelerated from rest from the positively charged plate X to the negatively charged plate Y.
At the mid-point between the plates, the proton has a kinetic energy EK. At this point, the alpha particle has a kinetic energy A.
.
B.
EK.
C.
2EK.
D.
4EK. (1)
43.
In the circuit below, the battery has negligible internal resistance. Three identical lamps L, M and N of constant resistance are connected as shown.
The filament of lamp N breaks. Which of the following shows the subsequent changes to the brightness of lamp L and lamp M?
Lamp L
44.
Lamp M
A.
stays the same
decreases
B.
increases
stays the same
C.
increases
decreases
D.
decreases
increases
The circuit contains a battery of e.m.f. 12 V and negligible resistance.
What is the potential difference across the 25 Ω resistor? A.
3.0 V
B.
4.5 V
C.
5.0 V
D.
7.5 V (1)
45.
A neutral conducting sphere is placed far away from a smaller, positively charged conducting sphere. The spheres are joined for a short period of time by a metallic wire. How do the charge and the electric potential of the spheres compare after the wire is removed?
Charge
Electric Potential
A.
different
different
B.
different
same
C.
same
different
D.
same
same (1)
46.
Three networks X, Y and Z are shown below. Each resistor has the same resistance.
Which list shows the network resistances in increasing order of magnitude? least → greatest
A.
X
Y
Z
B..
Y
X
Z
C.
Y
Z
X
D.
Z
X
Y
47. A proton of mass m and charge e is accelerated from rest through a potential difference V. The final speed of the proton is
A.
48.
B.
C.
D.
A positively charged rod is brought close to an earthed sphere S, as shown below.
The earth connection to the sphere is removed and then the charged rod is removed. The sphere S is found to be negatively charged. Which one of the following describes the material of S and the movement of charge between S and earth?
Material of S
Movement of charge
A.
conductor
negative charge moves from earth to S
B.
insulator
negative charge moves from earth to S
C.
conductor
positive charge moves from S to earth
D.
insulator
positive charge moves from S to earth
49.
The diagram below shows electric field lines in a region of space.
Which of the following diagrams best shows the variation with distance d of the potential V
along the line XY?
(1)
50.
The electric field strength at a point may be defined as A.
the force exerted on unit positive charge placed at that point.
B.
the force per unit positive charge on a small test charge placed at that point.
C.
the work done on unit positive charge to move the charge to that point from infinity.
D.
the work done per unit positive charge to move a small test charge to that point from infinity. (1)
This question is about electrical resistance. (a)
Define electrical resistance . ................................................................................................................................... ................................................................................................................................... (1)
(b)
(i)
Three resistors, each of resistance 6.0 Ω, are connected as shown below.
Calculate the total resistance between point A and point B of this arrangement. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (1)
(ii)
The arrangement in (b)(i) is now connected to two more resistors, as shown below. Each resistor is of resistance 6.0 Ω.
Using your answer in (b)(i), deduce that the total resistance between point C and point D is 8.4 Ω. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(iii)
One of the resistors in the arrangement shown in (b)(ii) becomes faulty. The resistance between point C and point D is found to be 6.0 Ω. On the diagram in (b)(ii) above, identify the faulty resistor by drawing a circle around it. Deduce the nature of the fault.
......................................................................................................................... (2) (Total 6 marks)
32.
This question is about electric circuits. (a)
Define emf and state Ohm’s law. emf: ............................................................................................................. ............................................................................................................. Ohm’s law:
............................................................................................................. ............................................................................................................. (2)
)
In the circuit below an electrical device (load) is connected in series with a cell of emf 2.5 V and internal resistance r. The current I in the circuit is 0.10 A.
The power dissipated in the load is 0.23 W. Calculate (i)
the total power of the cell; ......................................................................................................................... ......................................................................................................................... (1)
(ii)
the resistance of the load; ......................................................................................................................... .........................................................................................................................
......................................................................................................................... ......................................................................................................................... (2)
(iii)
the internal resistance r of the cell. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(c)
A second identical cell is connected into the circuit in (b) as shown below.
The current in this circuit is 0.15 A. Deduce that the load is a non-ohmic device. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (4) (Total 11 marks)
37.
This question is about electric circuits. (a)
(i)
Define emf and state Ohm’s law.
emf: .................................................................................................... .................................................................................................... Ohm’s law: .................................................................................................... .................................................................................................... (2)
(ii)
The graph below shows the I-V characteristic of a particular electrical component.
State show the resistance of the component is determined from the graph. ......................................................................................................................... ......................................................................................................................... (1)
(b)
In the circuit below an electrical device (load) is connected in series with a cell of emf 2.5 V and internal resistance r. The current I in the circuit is 0.10 A.
The power dissipated in the load is 0.23 W. Calculate
(i)
the total power of the cell; ......................................................................................................................... ......................................................................................................................... (1)
(ii)
the resistance of the load; ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(iii)
the internal resistance r of the cell. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... .........................................................................................................................
(c)
A second identical cell is connected into the circuit in (b) as shown below.
The current in this circuit is 0.15 A. Deduce that the load is a non-ohmic device. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (4) (Total 12 marks)
48.
Electricity Static electricity (a)
By reference to the movement of charge in a metal and in plastic, explain the electrical properties of conductors and insulators. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(b)
A gold-leaf electroscope is positively charged. (i)
Explain why the electroscope has an electric potential with respect to Earth. ......................................................................................................................... .........................................................................................................................
......................................................................................................................... (2)
(ii)
Outline why there is no electric field inside the metal cap of the electroscope. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(iii)
A student touches the metal cap of the electroscope. Describe the movement of charge that occurs. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
Current electricity (c)
In order to investigate the variation of the current I in a variable resistor with the potential difference V across it, a student set up the following circuit.
The variation of the current I with V is shown below.
Use the graph to deduce that, for the battery,
(i)
its emf is 4.5 V; ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(ii)
internal resistance is 1.2
Ω.
......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(d)
The battery in (c) is to be used as the power source for an electrical device. The device is rated as 0.8 V, 1.5 A. Complete the circuit below to show how the battery may be connected so that the device operates normally. Calculate the value of any other component you may use.
................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (4)
(e)
An electric heater contains a number of similar heating elements, connected as shown to a supply of V volts. The switches S 1 and S2 are shown “open”.
Each heating element dissipates power P when connected to a supply of V volts. The resistance of each element may be considered to be constant.
Complete the table below to give the total power dissipated, in terms of P, for the switches in the positions indicated.
Switch S1
Switch S2
closed
closed
closed
open
open
open
Total power
(3) (Total 20 marks)
51.
Static electricity (a)
By reference to the movement of charge in a metal and in plastic, explain the electrical properties of conductors and insulators. ................................................................................................................................... ................................................................................................................................... ...................................................................................................................................
(b)
A gold-leaf electroscope is positively charged. (i)
Outline why there is no electric field inside the metal cap of the electroscope. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(ii)
A student touches the metal cap of the electroscope. Describe the movement of charge that occurs. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
59.
Electric circuits (a)
The diagram below shows the circuit used to measure the current-voltage ( I-V)
characteristic of an electrical component X.
On the diagram above, (i)
label the ammeter A and the voltmeter V. (1)
(ii)
mark the position of the contact of the potentiometer that will produce a reading of zero on the voltmeter. Label this position P
b)
The graph below shows the current-voltage ( I-V) characteristics of two different conductors X and Y.
(i)
State the value of the current for which the resistance of X is the same as the resistance of Y and determine the value of this resistance
Current:
.....................................................................................................
Resistance: ..................................................................................................... (2)
(ii)
Describe and suggest an explanation for the I-V characteristic of conductor Y. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (3)
(c)
The two conductors X and Y are connected in series with a cell of negligible internal resistance. The current in the conductors is 0.20 A. Use the graph in (b) to determine (i)
the resistance of Y for this value of current; ......................................................................................................................... ......................................................................................................................... (1)
(ii)
the emf of the cell. ......................................................................................................................... ......................................................................................................................... (Total 10 marks) 74.
(2) Electrical circuits
Andrew is set the task of measuring the current-voltage ( I-V) characteristics of a filament lamp. The following equipment and information are available.
Information Battery
emf = 3.0 V, negligible internal resistance
Filament lamp
marked “3 V, 0.2 A”
Voltmeter
resistance = 30 k Ω, reads values between 0.0 and 3.0 V
Ammeter
resistance = 0.1 Ω, reads values between 0.0 and 0.5 A
Potentiometer
resistance = 100
(a)
Ω
For the filament lamp operating at normal brightness, calculate (i)
its resistance; ......................................................................................................................... ......................................................................................................................... (1)
(ii)
its power dissipation. ......................................................................................................................... ......................................................................................................................... (1)
Andrew sets up the following incorrect circuit.
(b)
(i)
Explain why the lamp will not light. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... (2)
(ii)
State the approximate reading on the voltmeter. Explain your answer. ......................................................................................................................... .........................................................................................................................
......................................................................................................................... c)On the circuit diagram below, add circuit symbols to show the correct position of the ammeter and of the voltmeter in order to measure the I-V characteristics of the lamp.
(2)
(d)
On the axes below draw a sketch graph to show the I-V characteristics for this filament lamp.
(4)
(e)
Explain the shape of the graph that you have drawn in (d). ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (2) (Total 14 marks)
82.
This question is about electrical components. (a)
In the space below, draw a circuit diagram that could be used to determine the currentvoltage (I-V) characteristics of an electrical component X.
(2)
The graph below shows the I-V characteristics for the component X.
The component X is now connected across the terminals of a battery of emf 6.0 V and negligible internal resistance. (b)
Use the graph to determine (i)
the current in component X; ........................................................................................................................... (1)
(ii)
the resistance of component X. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2)
A resistor R of constant resistance 2.0 Ω is now connected in series with component X as
shown below.
(c)
(i)
On the graph in (a), draw the I-V characteristics for the resistor R. (2)
(ii)
Determine the total potential difference E that must be applied across component X and across resistor R such that the current through X and R is 3.0 A. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2)
(d)
(i)
A resistor is to be used as a temperature-measuring device. List two desirable properties of such a device. 1. ....................................................................................................................... 2. ....................................................................................................................... (2)
(ii)
Explain how a temperature scale could be constructed for this resistance thermometer. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3) (Total 14 marks)
90.
This question is about electric circuits. Susan sets up the circuit below in order to measure the current-voltage ( I-V) characteristic of a small filament lamp.
The supply is a battery that has an emf of 3.0 V and the ammeter and voltmeter are considered to be ideal. The lamp is labelled by the manufacturer as “3 Volts, 0.6 Watts”.
(a)
(i)
Explain what information this labelling provides about the normal operation of the lamp. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2)
(ii)
Calculate the current in the filament of the lamp when it is operating at normal brightness. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2)
Susan sets the variable resistor to its maximum value of resistance. She then closes the switch S and records the following readings. Ammeter reading = 0.18 A
Voltmeter reading = 0.60 V
She then sets the variable resistor to its zero value of resistance and records the following readings. Ammeter reading = 0.20 A
(b)
(i)
Voltmeter reading = 2.6 V
Explain why, by changing the value of the resistance of the variable resistance, the potential difference across the lamp cannot be reduced to zero or be increased to 3.0 V. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2)
(ii)
Determine the internal resistance of the battery. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3)
(c)
Calculate the resistance of the filament when the reading on the voltmeter is (i)
0.60 V. ........................................................................................................................... ........................................................................................................................... (1)
(ii)
2.6 V. ........................................................................................................................... ........................................................................................................................... (1)
(d)
Explain why there is a difference between your answers to (c)(i) and (c)(ii). ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2)
(ii)
the resistance of the filament. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................
(1)
In order to measure the voltage-current (V-I) characteristics of a lamp, a student sets up the following electrical circuit.
(b)
On the circuit above, add circuit symbols showing the correct positions of an ideal ammeter and an ideal voltmeter that would allow the V-I characteristics of this lamp to be measured. (2)
The voltmeter and the ammeter are connected correctly in the previous circuit. (c)
Explain why the potential difference across the lamp (i)
cannot be increased to 12 V. ........................................................................................................................... ........................................................................................................................... (2)
(ii)
cannot be reduced to zero. ........................................................................................................................... ........................................................................................................................... (2)
An alternative circuit for measuring the V-I characteristic uses a potential divider . (d)
(i)
Draw a circuit that uses a potential divider to enable the V-I characteristics of the filament to be found.
(3)
(ii)
Explain why this circuit enables the potential difference across the lamp to be reduced to zero volts. ........................................................................................................................... ........................................................................................................................... (2)
The graph below shows the V-I characteristic for two 12 V filament lamps A and B.
(e)
(i)
Explain why these lamps do not obey Ohm’s law. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (2)
(ii)
State and explain which lamp has the greater power dissipation for a potential difference of 12 V. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (3)
The two lamps are now connected in series with a 12 V battery as shown below.
(f)
(i)
State how the current in lamp A compares with that in lamp B. ........................................................................................................................... ........................................................................................................................... (1)
(ii)
Use the V-I characteristics of the lamps to deduce the total current from the battery. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... (4)
(iii)
Compare the power dissipated by the two lamps. ........................................................................................................................... ........................................................................................................................... (2) (Total 25 marks)
