X CBSE PHYSICS | ELECTRICITY – QUESTION BANK
X CBSE PHYSICS Electricity Question Bank Q1.
A given piece of a wire length L, cross-sectional area A and resistance R is stretched uniformly to a wire of length 2 L. What W hat will be the new resistance?
Q2.
A current of 4 A flows through a 12V car head light bulb for 10 minutes. How much energy transfer takes place during this time?
Q3.
If the current in an electric bulb drops by 2%. Find the % decrease in power?
Q4.
A wire of resistance 2 is redrawn so that its length becomes 4 times. Find the resistance of the redrawn wire.
Q5.
What is the Fuse wire?
Q6.
Why is very less quantity of heat energy produced in the connecting wires?
Q7.
Which one has more resistance 100 watt bulb or 60 watt bulb?
Q8.
How much energy is given to each coulomb of charge passing through a 6V battery?
Q9.
What determines the rate at which energy is delivered by a current?
Q10. What does an electric circuit mean? Q11. Name a device that help to maintain a potential difference across a conduct. Q12. Judge the equivalent resistance when the following are connected in parallel (a) 1W and 10
6
W
(b)1W and 103 W and 106 W Q13. Define the term electric energy. Write an expression for the electric energy consumed in an
electric circuit. Q14. What is meant by power-rating of an appliance? A bulb is rated as 60 W, 220 V. What does it
indicate? Q15. Let the resistance of an electrical component remains constant while the potential difference
across the two ends of the component decreases to half of its former value. What change will occur in the current through it? Q16. A piece of wire is drawn by pulling it unit is length is doubled. Compare the new resistance with
the original value. mathematically. Define S.I. unit of resistance. Q17. State ohm’s law. Express it mathematically. Q18. Draw a circuit diagram with a cell, an electric bulb, an ammeter and plug key.
t he heater (c) Q19. For a heater rated at 4kW and 220V, calculate (a) The current (b) The resistance of the The energy consumed in 2 hours. Q20. An electric lamp of 100 W, a toaster of resistance 50 W, and a water filter of resistance 500W are
connected in parallel to a 220 V source. What W hat is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it? 1|Page
Q21. What are the advantages of connecting electrical devices in parallel with the battery instead of
connecting them in series? Q22. How can three resistors of resistances 2 W, 3 W, and 6 W be connected to give a total resistance
of (i) 4W (ii)1 W? Q23. What is the terminal potential difference of a cell, when it is short-circuited? Q24. Write down the differences between conductors and insulators. Q25. What is the principle of conservation of electric charge? Q26. How will you connect three resistors of 2 , 3 and 5 respectively so as to obtain a resultant
resistance of 2.5? Draw the diagram to show the arrangement. Q27. What are superconductors? Explain. Q28. What is the Board of Trade (B. O. T.) unit? Q29. If the n parallel resistances of equal resistance are connected in series with n series resistances
of equal resistance then find the equivalent equivalent resistance of the combination. Q30. Give the five properties of electric charge.Write down the short note on power rating of a resistor. Q31. What are the differences between electrostatic potential and potential difference? Q32. What is electric charge? What are the types of electric charge? Explain. Q33. A 60- watt lamp is operated at 220-volt power line. What will be resistance when the lamp is
lighting? How much current will flow in it? Estimate, how much current will flow in the lamp when it is connected to a 2-volt battery? Q34. The resistance of two conductors in series is 40 and their resistance becomes 7.5 when
connected in parallel. Find the resistance of the each conductor. 3 ohm
Q35. In the following circuit find the ratio of
current in 3 and 1 resistance?
3A
a
1 ohm
b
6 ohm
c
Q36. What is coulomb force and coulomb's law? Explain. Q37. In a house there are 12 bulbs 440, one motor of 1/10 horse - power, and 4 fans each of 100
watt. These ore operated 5 hours per day. Find the expenditure of electricity in a month of 30 days if the cost of electricity is 50 paisa. Q38. State ohm's law of resistances. Explained by drawing circuit diagram and also define the term
'resistance'. Q39. Give the law of combination of resistances in parallel. With the help of a neat diagram drive the
formula for the equivalent equivalent resistance of three resistances connected in parallel. t he each. Q40. Explain a) Electric Power. b) Electric energy. Write the different units of the Q41. If two bulbs of power of P 1 and P2 are connected in series. What is total power consumed by the
circuit? 2|Page
Q42. A resistance 6 is connected in parallel with a resistance 3 . What resistance R must be
connected in series with the combination of 3 and 6 so that the equivalent resistance is equal to the resistance 3? Q43. Two resistances in parallel, X
Y of unknown value, are connected in series with a third
resistance Z ends of resistance C is 180 V and the power in the
X = 2 0 I
complete circuit is 3600 W. Calculate:
1 I 2 I
(a) The value of resistance Y.
Y
Z = 1 2
I 1 8 0 V
(b) The current in each resistance. (c) The voltage applied to the ends of the whole circuit. Q44. Define one Ampere. Q45. What is relation between V, W, Q? Q46. In a residential house, the following loads are connected:
(i)
6 lamps of 40 W each, switched on for 5 hours a day.
(ii)
2 fans of 60 60 W each, switched on for 12 hours a day.
(iii)
100 W of a heater heater working for 2 hours a day. day.
(iv)
A refrigerator refrigerat or of 250 W w working orking for 10 hours a day.
If each unit of energy costs Rs. 2.30, what will be the total expenditure on electricity of that house in a month of September? equivalent resistance of following circuit. Q47. Find the equivalent 1.5
1.5 2
1.5
1.5
1.5
1.5
2
1
2 2
0.5
1.5
A
B
Q48. If the length of conductor wire is doubled and radius of cross section area is half than, what will be
the resistance of conductor becomes? Q49. What is unit of resistivity?What do you mean by the open circuit and closed circuit?
t he cell? Q50. What is the direction of the electric current in the circuit and in the Q51. What do you mean by power - rating of a resistor? Q52. State the charge carriers in the liquids, gases and in semiconductors? Q53. A parallel combination of three resistors takes a current of 7.5 A from a 30 V supply. If the two
resistors are 10 and 12, calculate the third resistance. Q54. A heater coil connected to a 220 V has a resistance of 150 . How long will it take for this coil to
heat 1kg of water from 20 C to 60 C, assuming that all heat is taken up by water? 3|Page
Q55. What do you understand by Electric energy? Explain the B.O.T unit and Rule for calculation of
cost of power. Q56. Give the 4 properties (physical (physical facts) of each of series and parallel combination of resistances? Q57. A resistance 6 is connected in parallel with a resistance 3 . What resistance R must be
connected in series with the combination of 3 and 6 so that the equivalent resistance is equal to the resistance 3? 30 ohm
Q58. What is the net resistance between points A and 2 ohm
B in the t he following circuit?
7 ohm
Q59. Derive the expression for heat produced in a
15 ohm
A
B 60 ohm
conductor due to current flow trough it. Q60. Draw a schematic diagram of a circuit consisting of a battery of four 2 volt cells. A 5 ohm resistor,
an 8 ohm resistor and a 12 ohm resistor and a plug key all connected in series. Q61. A copper wire has a diameter of 0.5 mm and a resistivity of 1.6 x
10
6
cm.
How much of this wire
would be necessary to make a resistance of 10 ohm? Q62. What is the main purpose of earthing of electrical appliance? Q63. The resistance of two conductors in series is 40 ohm and their resistance becomes 7.5 ohm,
when connected in parallel. Find the resistances of each. Q64. An electrical heater is rated 4 KW, 220 V, Calculate: (i) The current (ii) resistance of the heater (iii)
Energy consumed in 2 hrs. (iv) Total cost if 1 KWH is charged at Re. 0.50. Q65. Define electric energy and electric power. What are their units?
Q66. In the Circuit given, Calculate:
(i)
Equivalent Equivalent resistance of the circuit.
(ii)
Total current in the circuit.
(iii)
Potential difference across each resistor.
R2 R3
R1
I
I I
6V
I
Q67. What do you understand by heating effect of electric current? A water heater is rated at 220 V-
2kW. This heater is used for heating 20kg of water, which is initially at 20 C. If the heater is switched on for 15 minutes, what will be the final f inal temperature of water? If C=4200J/kg/ C. Q68. A metal plate of surface area 250 sq. cm is to be coated on both sides with copper by electrolysis.
How long will it take to deposit 0.01cm in thickness if a current of 1.5 Amp is used? (E.C.E of copper = 0.00033 gm/C, density of copper = 9 g cm -3) Q69. The maximum power rating of a 20
resistor is 2.0 kW. (This is the maximum power the resistor
can dissipate as heat, without melting or changing in some other undesirable way). Would you connect this resistor directly across a 300 V d.c. source of negligible resistance? Explain your answer. 4|Page
Q70. Out of the following bulbs rated 40W, 220V, 60W, 220V and 100W, 220V which one will give the
brightest when connected in series to a supply of 220V? Q71. Read the following statements carefully and write whether the statement is true or false:
(i)
The quantity of of charge flowing past a point multiplied by time is current.
(ii)
The flow of charge through a conducting conducting wire connected connected to a cell cell is the result result of chemical chemical reaction inside the cell.
(iii)
The resistivity resistivity of all pure metals increases with increase increase in in temperature. temperature.
(iv)
Ohm's law is a relation relation between the power used in a circuit to the current current and the potential potential difference.
(v)
A series circuit has has only one conducting conducting path path for the electrons that move through it; a parallel circuit has multiple conducting paths.
(vi)
A conducting conducting wire offers resistance resistance to the flow of electrons electrons because because electrons repel each other in the wire.
equivalent resistance of the circuit as shown in Figure in which six 1 Q72. Calculate the equivalent
resistors are
connected in hexagonal form. R2 R1
R3 B
A R4
R6 R5
Q73. The resistance of each of the three wires joined as in the
fig. is 2
, and each one can have maximum power of 18
2
watt (other wise it will melt). Find the maximum power
2
2
the whole circuit can take.
Q74. A certain piece of copper having length L & A is cross-section area. If it is to be shared into a
conductor of minimum resistance. What will be Its length and diameter. Q75. What is Ohm's law? Explain how it is used to define the unit of resistance. Q76. Give the law of combination of resistances in parallel. Obtain the relation for the equivalent
resistance of three resistances connected in parallel. Q77. Q78. A heater is designed to operate with a power of 1000
watt in a 100-volt line. It is connected to two
1000 watt Heater 10 ohm R
resistance of 10 ohm and R ohm as shown in the figure. If the heater is now giving a power of 62.5 watt. Find the value of the unknown resistance.
100 Volt
5|Page
Q79. Two resistances in parallel, R1 of 20Ω and R2 of unknown value, are connected in series with a
third resistance R3 of 12Ω. The supply to the circuit is direct current. If the potential difference across the ends of resistance R3 is 180 V and the power in the complete circuit is 3600 W. Calculate: 180Volt
(a) The value of resistance R2. V
(b) The current in each resistance. (c) The voltage V applied to the ends of the whole circuit. -----
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