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Physics for engineers PHYS 1422
Lab 3: ohm’s Law
Nouf AlQAhtani
201100868
November 12th, 2012
This lab will study the elements that obey Ohm’s Law and to verify the rules
for resistors arranged in parallel or in series.
Formula:

Ohm’s Law says that a value of electric field current in a piece of
conductor depends nearly in the electric potential applied to it.
(I=V/R)

Where R= electric resistance that depends on the material forming the
conductive element, but does not depend on the applied potential.

The flow of current through each element of the circuit is completely
characterized by the total applied voltage and the resistance of the
individual resistors.
Equipment needed:
Resistor, power supplies, ampmeter, voltmeter and cables.
Procedure:
Part 1: Ohm’s Law
We measure the potential difference V across the resistor and the current I.
1. Vary the voltage by the power supply and measure V and I by using the
voltmeter and ampmeter:
Current (I)
Voltage (V)
1.
0.05
5.1
2.
0.11
12.1
3.
0.15
15.6
2. The slope is 116.67
3. The percent Difference: %Diff = 16.67%
b
Part2: Resistors connected in series
We verify the rules for effective resistance connected in series, connected in
series 220 Ω and 100 Ω
1. We vary the voltage in the power supply and measure the current and the
voltage using the ampmeter and voltmeter respectively:
Current (I)
Voltage (V)
Voltage/Current
1.
0.015
5.1
340
2.
0.018
6.3
350
3.
0.021
7.1
338.1
4.
0.038
13.0
342.12
Average
=342.555
2. The percent Difference: %Diff = 7.03%
Part3: resistors connected in parallel
1. we vary the rules for effective resistance of resistors connected in parallel,
connect in parallel 220 Ω and 100 Ω:
Current (I)
Voltage (V)
Voltage/Current
1.
0.07
5.2
74.29
2.
0.13
9.8
75.38
3.
0.16
11.8
71.42
4.
0.12
15
73.75
Average
2. The percent difference: %Diff = 7.29%
73.71