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Palestine Polytechnic University
Collage of IT and Computer Engineering
Computer Systems Engineering Department
Electrical Circuits Lab
Experiment Title:
Potentiometer, Voltage Divider and Current
Divider currents
Experiment Number: 4
Date: 4 March 2013
Instructor:
Zahir Sa'afeen

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Objectives:
 To identify the use of potentiometer
 To be able to explain voltage distribution , current distribution ,
and the effect of a load on voltage divider using voltage and
current divider rule.
Equipments:
1. FACET base unit.
2. DC fundamental circuit board.
3. Digital Multimetre.
4. Wires.
5. Software (Multisim).
6. Potentiometer.
Theory:
 What is Potentiometer?
A potentiometer is a manually adjustable electrical resistor that uses three
terminals. In many electrical devices, potentiometers are what establish the
levels of output. For example, in a loudspeaker, a potentiometer is used to
adjust the volume. In a television set, computer monitor or light dimmer, it
can be used to control the brightness of the screen or light bulb.
 Workingof a potentiometer.
In a potentiometer an electrically conductive wiper slides across a fixed
resistive element.
One terminal of the potentiometer is connected to a power source, and
another is hooked up to a ground — a point with no voltage or resistance and
which serves as a neutral reference point. The third terminal slides across a
strip of resistive material. This resistive strip generally has a low resistance
at one end, and its resistance gradually increases to a maximum resistance at
the other end. The third terminal serves as the connection between the power
source and ground, and it usually is operated by the user through the use of a
knob or lever.

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 Voltage Divider Rule (VDR)
The voltage divider rule is very useful in determining the voltage drop across a
resistance within a series circuit.
The general form of VDR is : VRX = * VT , where RT : total resistance
across series circuit , and Rx is the resistance across which you are calculating
voltage drop.
 Current Divider Rule (CDR)
The current divider rule is useful in determining the current flow through one
branch of a parallel circuit.
The general form of CDR is: IRX = * IT, where RT: total resistance of the
parallel branch under examination.

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Calculations and Analysis:
Exercise 1:
(Using color code)
R1 = 910 ± 5% Ω
R2 = 1600 ± 5% Ω
R3 = 160 ± 5% Ω
R4 = 16,000 ± 5% Ω
Exercise 2:
IR2 = = = 4.87 mA
IR4 = = 4.87 mA
IR1 = IR2 + IR4 = 9.74 mA
Experimental circuits and exercises:
Exercise 1: Voltage Divider

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The Potentiometer

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Graphs

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Conclusions:
 Series circuits proportion, the total supply voltage among individual voltage
drops, the proportions being strictly dependent upon resistances: VRx = VTotal
(Rx / RTotal)
 When two resistors are in parallel, the current flow across a resistance: IR1 =
(R2/RTotal )* IT
 A potentiometer is a variable-resistance component with three connection
points, frequently used as an adjustable voltage divider.
 We have a knowledge about using potentiometer and how the resistance
changed when we tap the tapper .