To Investigate the Resistance of a Wire Using the Equation V=ir

Aim

To investigate the resistance of a wire using the equation V=IR

Prediction

I predict that resistance will be directly proportional to the length of the wire.

*P.6a/P.8a

Apparatus

* Voltmeter

* Ammeter

* Piece of wood

* Copper wire (100cm)

* Crocodile clips

* Connecting wires

* 2 Cells

Diagram

Method

* I am going to have my experiment all set out with the apparatus as in the diagram above. The copper wire of 100cm connected firmly to the piece of wood (wood is used as it will not interfere and not conduct.

* I will then connect everything up except for the cells with the connection wires.

* Then I will put the crocodile clips at 10 cm of the copper wire

* Then the connection wires will be connected to the cells until a firm reading of Current and Voltage is read.

* This will only be a short time as it may begin to heat up as the electrons will flow quickly between 10cm of wire and will not take as long, which would cause my results to be inaccurate.

* This will be repeated at 10-90 cm and then repeated a further 3 times

* When I get to 90 cm and I connect the wire I will have to do it very quickly as the wire will be shortest and will heat up immediately. By controlling it which keeps it a fair test.

* The results will be recorded and then I will work out the resistance by using the equation resistance = Voltage/Current, R= V/I

Results

Result number Length (cm) Current (A) Voltage (V) Resistance

(R) Ω

1 2 3 Av 1 2 3 Av

1 10 0.60 0.70 0.60 0.60 0.52 0.46 0.83 0.50 0.83

2 20 0.35 0.20 0.35 0.30 0.70 0.65 0.64 0.67 2.23

3 30 0.27 0.18 0.28 0.24 0.79 0.71 0.75 0.71 3.00

4 40 0.19 0.16 0.22 0.19 0.85 0.82 0.83 0.83 4.37

5 50 0.17 0.16 0.19 0.17 0.86 0.87 0.90 0.88 5.18

6 60 0.15 0.15 0.17 0.16 0.88 0.90 0.98 0.92 5.75

7 70 0.12 0.14 0.14 0.13 0.93 1.04 1.03 1.00 7.69

8 80 0.10 0.12 0.19 0.14 0.99 1.08 1.19 1.09 7.79

9 90 0.10 0.11 0.11 0.11 1.00 1.10 1.03 1.04 9.45

Analysis

The evidence I have obtained shows a straight line, known as a line of best fit, which indicates that