Investigating weather the length of a wire affects the resistance.

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Doha Salameh        Physics coursework

11JCU               Mr Harris

GCSE Science Coursework Investigation

Electricity

Investigating the resistance of a wire

Introduction

I am investigating weather the length of a wire affects the resistance.

The main factors that affect the resistance of a wire are length, thickness, material of wire, voltage and temperature. Resistance occurs in all parts of the circuit, that is when particles collide with something opposing it therefore this will slow down the flow of electric current. George Ohm, a German schoolmaster stated that the relationship between the length of the wire and the resistance should be directly proportional, which means that if the length increases then the resistance must also increase. To calculate the resistance of a wire you divide the current into the voltage. R (ohms) = V/A.

Planning

 I am going to be doing two experiments for this investigation. The first will be just to test if the circuit works and the second experiment is the main investigation, which is to find out weather the length of a wire affects the resistance. Circuit 1 is the circuit that I will be applying for the investigation. Circuit 2 is the trial experiment, to test if the circuit works.

Diagrams

     

Equipment

  • Meter Ruler
  • Wire (100cm)
  • Power Pack
  • Ammeter
  • Volt Meter
  • 2 Crocodile Clips

Method

  1. Collect equipment and set up circuit as shown in the diagram.
  2. Attach a wire from the power pack to the switch.
  3. Place another wire from the switch to the bulb.
  4. Place another wire from the bulb to the ammeter.
  5. Measure 100cm of wire, then tape it to the meter ruler.
  6. Attach the crocodile clips from the wires to the power pack.
  7. Switch power pack to four volts. Circuit is now complete and the light bulb must light up, if it does not then there must be a fault in the circuit (faulty bulb etc.)
  8. To calculate the resistance of the wire, I have to ensure that the light bulb and the switch are placed in the circuit. This is the voltage divided by the current.
  9. Record readings of the current (A) and the voltage (V) at 100cm and reduce the length of the wire by 10 cm each time.
  10. To ensure the reliability of results I need to repeat the experiment two times and take the average readings for both the voltage and the current. I will round the readings to 2d.p.
  11.  I am then going to calculate the resistance (ohms) and arrange the outcomes in to a results table.
  12.  Finally I will construct two line graphs, these are a voltage vs. current graph for a wire and a resistance line graph.
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Fair test 

To make the experiment a fair test I will need to consider the following;

  • Variables like the length, voltage and the temperature have to keep constant throughout the experiment
  • Make sure I repeat the same experiment at least two times so that I have accurate results.
  • Make sure that the crocodile clips are placed as accurately as possible and they also have to be stable

If I ensure that I follow these procedures for making the investigation a fair test then I am more likely to outcome much more ...

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