GCSE Physics Coursework - Current in a Wire

Ohm’s Law: 

 “The current through a wire remains the same provided the temperature remains constant.”

Proposed Method

As previously discussed, the length of wire was the easiest to control and measure, so this is what I shall vary.

The following circuit was made to carry out the investigation:

1. One metre length of a wire is fixed to a metre rule.
   
2. The first crocodile clip is clipped to the wire at the 0cm position on the metre rule.
   
3. The second crocodile clip is clipped to the specific position depending on the required length of wire.
   
4. The power supply is turned on, with a constant voltage of 6 volts.
   
5. After waiting for 20 seconds for the temperature to become constant, the voltage and current are then read off the ammeter and voltmeter, and recorded.
   
6. The power supply is then turned off and the second crocodile clip is

                     moved to the next position and the values are taken down again.

7. The above steps are completed for each length and then the entire investigation is repeated 3 times for accuracy, and so that averages can be taken.

Safety Precautions:

There are no specific, unobvious safety precautions.

Predictions:

• The longer the wire, the higher the resistance. This is because the longer the wire, the more times the free electrons will collide with other free electrons, the particles making up the metal, and any impurities in the metal. Therefore, more energy is going to be lost as heat in these collisions, thus raising the temperature and by Ohm’s Law the resistance will increase, thus the opposition to current increases and the current decreases.
  
• Doubling the length of the wire will result in double the resistance, meaning half the current. This is because by doubling the length of the wire one is also doubling the collisions that will occur, thus doubling the amount of energy lost in these collisions.

Proportionality:

Current is inversely proportional to the Length of Wire.
Resistance is directly proportional to the Length of Wire