Ohm’s Law Lab
Purpose: To study the relationship between voltage and current when a circuit contains a
resistor
Method:
1. Resistor#1 was obtained and the circuit was set up with the ammeter measuring the
current between the power source and the resistor. As that was done, the voltmeter was
then connected to measure the potential difference around the resistor.
2. The power supply was not to be plugged in until the set up was inspected by the
instructor.
3. The current was than being measured and recorded into the observation chart as the
voltage of the circuit was started at 3.0V.
4. After that had finished, the voltage was increased by 1.0V and measured once more.
This step was repeated till a maximum of 15.0V
5. Resistor # 2 replaced resistor #1 as the first resistor was placed aside to cool down.
6. Steps 3 and 4 were then repeated for the second resistor.
SAFETY ALERT: Do not touch any bare wires or connectors the power is turned on
Keep all equipment away from water
The resistor will be hot after you use it.
Materials:
 Power supply
 Red Resistor
 Green Resistor
 Two Multimeters
 Conducting Wires
Observations:
Green Resistor
16
Voltage (Volts)
14
12
10
8
6
4
2
0
0
0.05
0.1
0.15
Current (A)
0.2
0.25
0.3
Current Voltage V/I=R
(A)
(Volts)
0.05
3
60 Ω
0.07
4 57.14Ω
0.09
5 55.56Ω
0.11
6 54.55Ω
0.13
7 53.85Ω
0.15
8 53.33Ω
0.17
9 52.94Ω
0.19
10 52.63Ω
0.21
11 52.38Ω
0.23
12 52.17Ω
0.24
13 54.17Ω
0.26
14 53.85Ω
0.28
15 53.57Ω
Resistance average= 54.32Ω
Red Resistor
16
Voltage (Volts)
14
12
10
8
6
4
2
0
0
0.05
0.1
0.15
0.2
0.25
0.3
Current (A)
Current
(A)
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
0.11
0.12
0.13
0.13
0.15
Voltage
(Volts)
3
4
5
6
7
8
9
10
11
12
13
14
15
Resistance Average: 100.59 Ω
Comparing Both Resistors
Green Resistor VS Red Resistor
16
Voltage (Volts)
14
12
10
8
Green Resistor
6
Red Resistor
4
2
0
0
0.05
0.1
0.15
Current (A)
0.2
0.25
0.3
V/I=R
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
100 Ω
107.69Ω
100 Ω
Schematic Drawing
Analysis:
4.
What do you notice about the V/I values in your table? Calculate the average V/ I
for each resistor
The resistance (V/I) values in the two tables are similar. This is because the resistance
values range between 52 and 60 for the first resistor while the resistance values range between
100 and 107 for the second resistor. These results indicate that both ranges are equivalent to
each other. When comparing the average resistance of the two resistors; the average
resistance of the first resistor is around half of the average resistance of the second resistor.
The green resistor had an average resistance of 54.32 and the red resistor had an average
resistance of 100.59.
5.
A) Look at your graphs, by comparing steepness and by calculating slope, determine
which of the resistors produced a graph with the highest slope?
𝑦 −𝑦
To calculate slope of the each resistor, the formula 𝑋2 −𝑋1 would be used, these letters
2
1
can be subsisted by any 2 y and x values on the graph. In this case, our x value was the current
and the y value was the voltage. Using this formula, the slope of the first graph (green resistor)
5−4
is 5. This is because y2= 5, y1=4, x2= 0.9, and x1=0.7 ( 0.9−0.7 ). As the points have been
1
chosen and placed using the formula, subtraction occurs giving us an answer of 0.2 . Once the
answer has been given, the fraction must be simplified which gives the answer of 5. Therefore,
5 is the slope of the first graph (green resistor). The slope of the second graph (red resistor) is
10. This is because y2=5, y1= 4, x2=0.5, and x1=0.4. Once the points our found, the numbers
5−4
1
are put into formula form (0.5−0.4.) Then again subtraction occurs giving an answer of0.1. The
fraction is then simplified which resolves the answer of 10. Thus, the slope of the second graph
(red resistor) is 10. Since the slope of the second graph is 10 and the slope of the first graph is
5, the second graph has a higher slope. Moreover, the second graph (red resistor) also has a
steeper line compared to the first graph (green resistor).
B) How does your comparison of slope relate to the numbers you calculated in question
4?
The slope of the resistors is the same or almost the same as the average V/ I values.
This is because the average V/I values are calculated by dividing voltage by the current of all
the points, and then averaged out. Slope is familiar with this since slope is calculated by dividing
rise over run. The rise is the voltage and the run is the current. However, with slope there is no
need to average out because the slope is the average resistance of the resistor. Furthermore,
the averaged resistance of the red resistor was resolved to be approximately half of the green
resistor. When finding slope, the slope of the green resistor was also half the slope of the red
resistor.
C) What does the slope or the average V/I represent?
The slope and the average V/1 represent the same thing, which is resistance.
Resistance is the ability of a substance to resist the flow of electricity; it is measure in units
called Ohms, (Ω).
Conclusion:
Thus, the two resistors had different ways to impede the flow of electrons. The green
resistor averaged a resistance of 54.32 Ω while the red resistor averaged a resistance
of100.59Ω. These results conclude that the ability of the red resistor to resist flow of electrons
was approximately twice as much as the green resistor. The logical reason for this may be that
the red resistor had better insulating material than the green resistor. Conversely, the graphs
analysis showed that the red resistor has a steeper slope as well. The values from the two
slopes had an equivalent relation to the average resistance of both resistors; the red resistor
was twice as much as the green resistor. Overall, the red resistance was superior the green
resistor in resisting the flow of electrons.
OHM’S LAW LAB
Shawn Nagra
Romaan Naeem
11.16.11