VOLTAGE AND CURRENT DIVISION
Mhlanga S 23721804 and Dlamini L.S 23772727
Experiment Done 13/ 03/ 2013
ABSTRACT
An experiment to verify the properties of voltage and current division is presented. The voltage divider
is created using two resistors connected in series in a circuit. The current divider is created using 2
resistors connected in parallel. It is found that if one of the resistors in the voltage divider is greater
than the other, more voltage will be dropped across it. It is also found that the greater the resistor is,
less current will pass through. Experimental, simulated and calculated results are found to be in good
agreement.
1
TABLE OF CONTENTS
1.
INTRODUCTION………………………………………………………………………………………………………2
2.
THEORY…………………………………………………………………………………………………………..…3, 4
3.
PROCEDURE…………………………..………………………………………………………………………………5
4.
RESULTS AND DISCUSSION……………………………………………………………………………………..6, 7
5.
CONCLUSION………………………………………………………………………………………………………….8
6.
REFERENCES………………………………………………………………………………………………………….9
1.
INTRODUCTION
The aim of the lab is to investigate the concepts of voltage and current division.
Voltage and current division is an application of Kirchhoff’s Laws. A voltage divider and a current
divider will be designed. In electronics or EET, a voltage divider (also known as a potential divider) is a
linear circuit that produces an output voltage (Vout) that is a fraction of its input voltage (Vin). Voltage
division refers to the partitioning of a voltage among the components of the divider. a current divider is
a simple linear circuit that produces an output current (IX) that is a fraction of its input current (IT).
Current division refers to the splitting of current between the branches of the divider. The currents in
the various branches of such a circuit will always divide in such a way as to minimize the total energy
expended [1]. In this experiment the voltage and current division properties will be verified. Slight
deviations are caused by experimental errors which include taking somewhat wrong readings due to
fluctuating values in the ammeter and voltmeter.
2
2.
THEORY
Voltage and current division allow us to simplify the task of analysing a circuit.
Voltage Division allows us to calculate what fraction of the total voltage across a series string
of resistors is dropped across any one resistor.
.
For the circuit of Fig.1 voltage division formulas are:
V1 
R1 VS
( R1R2)
(1)
V2 
R2 VS
( R1R2)
(2)
Where V is the voltage and R is the resistance
Figure.1 Voltage divider circuit [2]. Used to measure what fraction of the total voltage is
dropped across any one resistor.
3
Current Division allows us to calculate what fraction of the total current into a parallel string of resistors
flows through any one of the resistors.
For the circuit of Fig.2 current division formulas are:
I1 
R2 IS
( R1R2)
(3)
I2 
R1 IS
( R1R2)
(4)
Where I is the current and R is the resistance
Figure.2 Current Divider circuit [2]
Current divider circuit used to calculate what fraction of the total current into a parallel string of
resistors flows through any one of the resistors.
4
3.
PROCEDURE
3.1 Voltage Division
The circuit was constructed as shown in Figure 3. The voltages v1 and v2 were measured by choosing
R1 = 5.6 KΩ, R2 = 1.5 KΩ and setting the variable power supply voltage Vs = 5V.
This step was repeated for R1 = R2 = 5.6 KΩ and the measurements were noted down. The voltages
V1 and V2 were calculated by using the formulas (1) and (2) in each case.
Figure.3 Voltage divider circuit [2]
3.2 Current division
A circuit was constructed as shown in figure 2. The currents Is, I1 and I2 were measured by choosing
R1 = 2.2 KΩ, R2 = 5.6 KΩ and Rs=1 KΩ .The variable power supply voltage was set at
Vs=10 V. This step was repeated by using R1=R2 =2.2 KΩ and the measurements were noted down.
Figure.4 Current divider circuit [2]
5
4. RESULTS AND DISCUSSION
4.1 Voltage Division Results
Tables 4.1, 4.2 and 4.3 show the calculated, simulated and experimental results.
Table 4.1 Calculated results
R(KΩ)
V1(v)
R1=5.6, R2=1.5
3.94
R1=5.6, R1=5.6
2.50
V2(v)
1.06
2.50
Table 4.2 Simulated results
R(KΩ)
V2(v)
R1=5.6, R2=1.5
3.94
R1=5.6, R1=5.6
2.50
V2(v)
1.06
2.50
Table 4.3 Experimental results
R(KΩ)
V1(v)
R1=5.6, R2=1.5
3.98
R1=5.6, R2=5.6
2.51
V2(v)
1.06
2.53
The voltage results convincingly seem to be in good agreement. The tables clearly indicate that the
calculated and simulated results were found to be the same. Slight deviations in the experimental
results might have been caused by fluctuating values in the ammeter making it hard to read precise
values. In addition, setting the voltmeter to exactly 10V on the Digital Lab also proved to be a difficult
task because the knob was too sensitive. If this experiment is to be redone, improvements can be
made by taking enough time to set the source voltage on the Digital Lab to the correct value.
6
4.2 Current Division Results
Tables 4.4, 4.5 and 4.6 show the calculated, simulated and experimental results.
Table 4.4 Calculated Results
R(Ω)
Is(mA)
R1=1, R2=2.2, R3=5.6
3.88
R1=1, R2=2.2, R3=2.2
4.76
I1(mA)
2.79
2.38
I2(mA)
1.09
2.38
Table 4.5 Simulated results
R(Ω)
R1=1 , R2=2.2 , R3=5.6
R1=1, R2=2.2, R3=2.2
Is(mA)
3.88
4.76
I1(mA)
2.79
2.38
I2(mA)
1.09
2.38
Table 4.6 experimental results
R(Ω)
Is(mA)
R1=1, R2=2.2, R3=5.6
3.89
R1=1, R2=2.2, R3=2.2
4.81
I1(mA)
2.79
2.42
I2(mA)
1.10
2.39
The calculated, simulated and experimental current results are also in convincing compliance. The
calculated and simulated results gave out corresponding values. On the other hand the experimental
results proved to be somewhat different from the calculated and simulated results. This might have
been caused by the fact that the ammeter that was used to measure the current would slightly alter the
values making it very possible to take wrong readings. If the experiment is to be redone, improvements
can be made by allowing the ammeter to settle to one value before taking readings to avoid taking
wrong reasons.
7
5.
CONCLUSION
An experiment to verify the properties of voltage and current division was presented. The voltage
divider was created using two resistors connected in series in a circuit. The current divider was created
using 2 resistors connected in parallel. It was found that if one of the resistors in the voltage divider
was greater than the other, more voltage was dropped across it. It was also found that the greater the
resistor was, less current passed through. Experimental, simulated and calculated results were found
to be in good agreement. Slight deviations were caused by experimental errors which included taking
somewhat wrong readings due to fluctuating values in the ammeter and voltmeter.
8
6.
REFERENCES
[1] http://en.wikipedia.org/wiki/Voltage_divider
[2] Circuit drawings taken from Electronics Laboratory Manual
http://www.wisc-online.com/Objects/ViewObject.aspx?ID=DCE3502
9