Introduction In this lab, we will understand the very basics of circuit cir cuit analysis. We will connect some series circuits and analyze them using Multisim as well on hardware. We will observe the effect of varying resistance on current while keeping voltage constant. We will also analyze the current in a series circuit and the effect of varying voltage on current. So our objective for this lab is to understand and analyze series circuit and the dependence of current, voltage and resistance on each other. he objective of lab also to be familiar with Multisim and
Theory Resistance in Series !omponent !omponentss of an electrical electrical circuit or electronic circuit can be connected in many different different ways. ways. he he two two simpl simples estt of these these are are calle called d serie seriess and and para paralle llell and and occu occurr fre"u fre"uen ently tly.. !omponents connected in series are connected along a single path, so the same current flows through all of the components. # circuit composed solely of components connected in series is known as a series circuit. In a series circuit, the current through each of the components is the same, and the voltage across the circuit is the sum of the voltages across each component. $ollowing circuit shows resistance in series.
$igure %.%
Relationship between current, voltage and resistance &oltage or electric potential difference in the conte't of (hm)s or *irchhoff)s laws is the difference in electric potential energy between two points per unit electric charge. #n electric current is a flow of electric charge. In electric circuits this charge is often carried by moving moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons. $inally, the electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. he inverse "uantity is electrical conductance, and is the ease with which an electric current passes. (hm+s (hm+s law is the basic law that govern governss the relationsh relationship ip between between voltage, voltage, curren currentt and resistance. (hm)s law states that the current through a conductor between two points is directl directly y propor proportio tional nal to the voltag voltagee across across the two points points.. Introd Introduci ucing ng the constan constantt of proportionality, the resistance, one arrives at the usual mathematical e"uation that describes this relationship. & I - where I is the current through the conductor in units of amperes, & is the voltage measured across the conductor in units of volts, and - is the resistance of the conductor in units of
ohms. More specifically, (hm)s law states that the - in this relation is constant, independent of the current.
$igure %. he above e"uation best e'plains the relationship between voltage, current and resistance. If voltage is kept constant and the resistance is doubled, the current is halved and vice versa. If the resistance is tripled the current becomes one third and so on. If the resistance is kept constant and voltage is increased the current also increases proportionally and vice versa. here is a direct relationship between voltage and current.
Results Part 1: Resistance in Series %. !alibrate the ohmmeter and measure the / resistors -% 001 ohm - 002 ohm -/ 010 ohm
$igure %
. Measure resistance from # to 3 !ircuit no. !ircuit % !ircuit !ircuit /
-ab4ohms5 00/ ohms %011 ohms 067 able %
Part 2: Controlling current by varying resistance %. 8se Multisim to simulate circuit 9,2,:.
Multisim Simulation !ircuit 9 XMM1
R1 V1 6V
1kΩ
!ircuit 2 XMM1
R1
R2
1kΩ
1kΩ
V1 6V
!ircuit : XMM1
V1 6V
R1
R2
1kΩ
1kΩ
R3 1kΩ
/. -ecord the value of current in circuit 9,2 and : in the table. !ircuit no. !ircuit 9 !ircuit 2 !ircuit :
-esistance 4able %5 &oltage 4&5 4ohms5 00/ : %011 2.1 066 :.% able
!urrent4m#5 !ircuit 9 2.0/ /.71 .72
Part 3: Current in a series circuit %. $ind the value of current in various location in circuit : and list them in table / ;ocation of multimeter (riginal ;ocation 3etween -% and - 3etween - and -/ 3etween -/ and common
!urrent 4m#5 .% .% .% .% able /
Part 4: Controlling current by varying voltage %. !onnect circuit and find current by vary input voltage and list the voltage and current values across the resistor in the table.
&oltage 4&5 1 : 9 7
!urrent 4m#5 1.9% :./ 9.%/ .%% 7 able 9
2. Make a graph of the values in the table
%&'alues $ # " ! 4 3 2 1 0
0
1
Multisim Simulations
2
3
4
!
"
#
$
XMM1
XMM2
R1 1kΩ
V1 8V
XMM3
XMM4
R2 1kΩ
V2 6V
XMM5
XMM6
R3 1kΩ
V3 4V
XMM7
XMM8
R4 V4 2V
1kΩ
V5
0V XMM10
R5 XMM9
1kΩ
Laboratory Questions Part 1: Resistance in Series /. Write a summary statement concerning resistance in series. When resistances are connected in series, the total resistance offered is the sum of all the resistance connected in series.
Part 2: Controlling current by varying resistance 1. Write a statement concerning controlling current by varying resistance. 3y increasing resistance, the current decreases when the voltage is kept constant. When the resistance was doubled the current halved and when it was increased to three times the current decreased to one third of the initial current.
Part 3: Current in a series circuit 9. Write a summary concerning controlling current in a series circuit. he current in constant in series in a circuit. It remains the same at every point in series.
Part 4: Controlling current by varying voltage :. Write a summary statement concerning current in series circuit. When the voltage is reduced the current also reduced given that the resistance is kept. he graph of voltage and current is a straight line indicating that they are directly proportional to each other.
Part : (uestions %.
It is connected in series in circuit to measure current. . What precautions must be observed while measuring current= $irst of it must be connected in series. If connected in parallel it may be damaged due to the flow of high current. Secondly, it must be connected depending on the correct scale on the >MM. $or current in amperes, it must be on the relevant scale for the measurement of the current /. #n ohmmeter must never be connected in circuit carrying current. Why= (hmmeter measures the resistance by applying a small voltage and producing a deflection according to the current flowing through it. If it is connected in a circuit carrying firstly it will not give the correct reading and if the current is large enough it may damage it. 9. Write a short statement concerning current, voltage and resistance in a series circuit and relationship of current and voltage with constant resistance. he voltage and current are directly proportional to each other. Increase in one "uantity causes increase in the other and vice versa provided that the resistance is constant. 3est way to e'plain it is by ohm+s law & I -
Conclusion In this lab, we observed that resistance in series act as a single of the value which is e"ual to the sum of the values of the resistance connected in series. *eeping the voltage constant, the current increases by decreasing current and vice versa. !urrent in a series circuit is same throughout and voltage and current are directly proportional to each other. I short, we studied the relationship between current, voltage and resistance and this relationship is e'plained by (hm+s law which is & I -
References https://en.wikipedia.org/wiki/Ohm's _ law https://en.wikipedia.org/wiki/Voltage https://en.wikipedia.org/wiki/Electric_current https://en.wikipedia.org/wiki/Electrical_resistance _and_conductance
