How Does Length Affect Resistance?

How does Length affect resistance?

Coursework

Aim

To find out how the length of a wire can affect resistance.

Factors affecting resistance

 Temperature

 Length of wire

 Thickness

 Type

Resistance is a force which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit.

Resistance is measured in ohms. The symbol for an ohm is Ω

Here is the rule for working out the resistance of a circuit: V/I = R or

V - Volts

I - current

R - resistance

Variables

* length of wire

* thickness

* type of wire

* current

* voltmeter

* temperature

Dependant variables

* length

Prediction

As we are looking at length this is my prediction:

I predict that the longer the wire the higher the resistance. This is because electrons have to travel pass more atoms and collisions between the electrons and atoms are made likely rather than in a shorter wire. Also I can say this because I know that the electrons have to compress together more in order to be able to pass through nichrome wire. The length of the wire will make a difference; this is because when you have a long wire, the electrons have to compress together for longer to be able to pass through the wire than they do in order to be able to pass through a short wire. I predict that the longer the wire, the greater the resistance. If I had a 30 cm wire and a 60 cm wire, the 60 cm wire would have a resistance twice that of the 30 cm wire.

Equipment

For this experiment I will be using a voltmeter, an ammeter, five wires, two crocodile clips, some nichrome wire and a power pack. The diameter of the wire will be kept the same so that it is a fair test. The voltage will also be kept the same, although the readings may not be exactly the same each time. I have chosen the following lengths:

20cm, 40cm, 60cm, 80cm and100cm

This is because these lengths have a fairly good gap between them which would facilitate me to efficiently compare my final results. Also this is because I can then see if my prediction about doubling the length is correct.

To make this test fair I should take more than one result so that I can work out an average, this will help prevent any erroneous results

Method

 First connect your wires from the battery pack to the variable resister which enables a control on the current.

 From the other side, connect the battery pack on to the ammeter.

 Then, have these both connected to the metal wire which should be connected in parallel to the voltmeter.

 Collect apparatus: a voltmeter, an ammeter, 5x wires, 2 crocodile clips, 20, 40, 60, 80 and 100 cm of nichrome and a power pack.

 Set apparatus up as shown:

Diagram

1. Set the power pack on as low a voltage as possible in order to prevent a high current passing through the circuit.

2. Place the 10 cm of nichrome between the two crocodile clips to complete the circuit.

3. Turn on the power pack and record what the ammeter and voltmeter read.

4. Replace the 10 cm of wire with the 20 cm of nichrome remembering to keep the voltage the same. Turn on your power pack and record what the ammeter and voltmeter say.

5. Change the wire to the 40 cm of nichrome wire and repeat the experiment for 60, 80 and 100cm

6. Work out the resistance for all the results using Ohm's law. V = I*R

7. Record your results in a table and a graph.

Table of Results

Reading 1

length variable resister voltmeter ammeter resistance (Ω)

20 0.5 0.5 0.49 1.02

40 0.5 0.5 0.26 1.92

60 0.5 0.52 0.18 2.8

80 0.5 0.63 0.17 3.71

100 0.5 0.73 0.15 4.86

Reading 2

length variable resister voltmeter ammeter resistance (Ω)

20 0.5 0.5 0.5 1

40 0.5 0.5 0.26 1.92

60 0.5 0.52 0.18 2.8

80 0.5 0.63 0.16 3.93

100 0.5 0.73 0.15 4.86

Reading 2

length variable resister voltmeter ammeter resistance (Ω)

20 0.5 0.5 0.49 1.02

40 0.5 0.5 0.26 1.92

60 0.5 0.52 0.18 2.8

80 0.5 0.63 0.16 3.93

100 0.5 0.73 0.15 4.86

Average Table of results