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# The aim of my experiment is to find out what happens to the resistance as an electrical current passes through different lengths of wire.

Extracts from this document...

Introduction

Physics Coursework

Resistance in wires

## Aim

The aim of my experiment is to find out what happens to the resistance as an electrical current passes through different lengths of wire.

## Prediction

I predict that the longer the piece of wire will cause an increase in resistance as the electrons will have a longer distance to travel so therefore more collisions occur due to more electrons passing through the wire. Resistance is the force, which resists the flow of an electric current around a circuit so that energy is required to push the particles around. It occurs when the travelling electrons collide with the atoms of the wire. When resistance is high conductivity consequently is low. Ohms law, V = I/R states that the higher the resistance means that more energy is used to pass through the wire meaning that there is a greater voltage if there is an increase in resistance so if the length is doubled the resistance will also double because there are twice as many electrons therefore twice the number of collisions occurring slowing the electrons down and making them use more energy to pass through the wire.

Middle

0

0.01

0

35

0

0.01

0

40

0

0.01

0

45

0

0.01

0

50

0

0.01

0

## Analysis of Preliminary Testing

For my first preliminary experiment I decided to test Constantine SWG 32 and SWG 26 with 3V(See Table 1). I used a voltmeter and an ammeter to work out the resistance at regular intervals of 5cm along the wire. I then worked out the resistance from the voltage and the current. I was pleased with the results that I received as they showed an obvious trend evolving. The results show that when the length of the wire is increased so does the resistance and the current.

Within my preliminary testing I noticed an anomalous result in my table for Constantine SWG 26 (See Table 1) where an obvious pattern can be seen emerging in the voltage passing through each wire. There is a continuous increase with each measurement until it reaches 50cm where it decreases. I believe the cause for this may well have been due to a change in temperature or some damage may have been caused to the wire. This is a problem I may have to consider for later testing.

I then decided to test both wires with a voltage of 5 but this constantly burnt and snapped my wires. To stop this from happening I decided to test each wire with 1V (See Table 3+4) but the readings were too low. My voltmeter gave me a constant reading of 0 for each wire and my ammeter gave me 0 until the last five readings which were all 0.01 amps.

I decided to use a power supply of 3V using both Constantine SWG 32 and SWG 26 measuring the voltage and current at intervals of 5cm up to 50cm. My preliminary testing has shown me that the wires must be changed constantly if they get to hot as it may affect its resistance. Heat causes the atoms in the wire to vibrate increasing the amount of collisions occurring.

## Methodology

#### Apparatus

Power Supply

Voltmeter

Ammeter

Wire (1m)

Crocodile clips

Meter rule

##### Step 1

Set up Circuit as below:

##### Step 2

Sellotape the wire along the meter rule. Place the positive crocodile clip at 0 and the negative at 5cm. Measure the volt and the current by taking the readings on the voltmeter and ammeter.

Step 3

To work out its resistance use this simple formula:

##### Step 4

Work out the resistance for the other following lengths]

10cm

15cm

20cm

25cm

30cm

35cm

40cm

45cm

50cm

## Obtaining Evidence

Results

Note: The following results are from an initial output of 3V from the power box

1st Test

## SWG 26

 Length of wire (cm) Voltage (v) Current (amps) Resistance (Ω) 5 0.2 1.7 0.1176471 10 0.4 1.4 0.2857143 15 0.5 1.3 0.3846154 20 0.6 1.2 0.5 25 0.75 1.1 0.6818182 30 0.8 1 0.8 35 0.9 1 0.9 40 1 0.9 1.1111111 45 1 0.9 1.1111111 50 1.1 0.8 1.375

## SWG 32

 Length of wire (cm) Voltage (v) Current (amps) Resistance (Ω) 5 0.5 1.3 0.3846154 10 0.8 1 0.8 15 1 0.9 1.1111111 20 1.2 0.9 1.3333333 25 1.3 0.7 1.8571429 30 1.4 0.6 2.3333333 35 1.5 0.5 3 40 1.55 0.5 3.1 45 1.6 0.4 4 50 1.7 0.4 4.25

Conclusion

## Evaluation

The main aim of my experiment was to find out what affect the length of a wire had in the resistance of a voltage

I believe my experiment went extremely well and it has provided me with clear and concise results that do not undermine my initial prediction and have me to construct reliable graphs.

Accuracy

To increase the accuracy of my experimentations I could do further testing on other factors that affect the resistance of a wire such as diameter or thickness to see when a piece of wiring is thick or thin how does this relate to its resistance. I could also use different wiring made from other materials e.g. copper to see if the number of free electrons and the number of electrons on its outer shell of the atom promote resistance.  I can also investigate the affect temperature has on its conductivity of electricity in a wire and to see why when there’s in increase in temperature there is also increase in the resistance.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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