Verifying the Effect of Length of a conductor to the Resistance

Vania Lundina – 11 Science

According to Ohm’s Law, the resistance of a conductor depends on its

material. From the formula R =  L / A, we can conclude that the

resistance of a conductor is directly proportional to its length, and is

inversely proportional to the cross-sectional area of the conductor

itself. The aim of this experiment is to verify the effect of length of a

conductor to its resistance.

My hypothesis would be the longer the material, the bigger the

resistance and the greater the cross-sectional area of the material,

the lower the resistance would be. The independent variable is the

length and thickness of the conductor. The dependent variable is the

voltmeter and ammeter reading to find the resistance, and the

controlled variable is the V from the power supply and the thickness

of the wire.

My experiment diagram would look like this:

A

V= Resistance wire

The materials needed are:

1. Resistance wires of 10 cm, 15 cm, 20 cm, 25 cm, 30 cm and

35 cm.

2. Connecting wires.

3. Crocodile clips.

4. A voltmeter.

5. An ammeter.

6. A power supply.

Procedures:

1. Set up the circuit with a 10 cm resistance wire like the diagram

shown above.

2. Turn the power supply on; set it into 3 V.

3. Check the reading on the ammeter and voltmeter.

4. Measure the resistance of the resistance wire using the formula

V = I R.

5. Do the same step for the resistances wire 15 cm, 20 cm, 25

cm, 30 cm and 35 cm.

In doing this experiment, the accuracy of the length of resistance wire

must be considered. To avoid any unexpected or inaccurate data, the

experiment will be repeated 3 times. I will take the average of the

three data.

Result in table form:

No

.

Length of

Resistance

wire/cm

Ammeter

Reading/A

Voltmeter

Reading/V

Resistance

from

R = V/I

Ave.

R/

TRIAL

1 2 3

1 10 1,8 1,3 1,6 0,7 0,7 1,0

2 15 1,5 1,6 1,1 0,9 0,9 1,0

3 20 1,4 1,7 1,2 1,2 1,2 1,2

4 25 1,2 1,8 1,5 1,5 1,5 1,5

5 30 1,1 2,0 1,8 1,9 1,7 1,7

6 35 1,0 2,1 2,1 2,1 1,9 2,0

Analysis and conclusion:

Some data form my first, second and third trial showed different

readings of ampere and volt. This difference might be caused by the

inaccuracy of the length of the resistance wire. But the average value

somehow proves the formula R =  L / A, where the length of the

resistance wire does affect the resistance of the conductor. So my conclusion

is, the longer the wire, the bigger the value of resistance would be.