Resistance of wires – assessed investigation Aim: To find out how the length of a wire affects its resistance. What you need to do: Choose a circuit to use. Choose a circuit to use. Plan your experiment so that it is a FAIR TEST. Plan your experiment so that it is a FAIR TEST. Take measurements of resistance for at least 6 different lengths of wire. Record your results in a table. Take measurements of resistance for at least 6 different lengths of wire. Record your results in a table. Repeat the experiment another 2 times (3 sets of results in total) Repeat the experiment another 2 times (3 sets of results in total) Calculate an AVERAGE resistance for each length of wire. Calculate an AVERAGE resistance for each length of wire. You could go on to plot graphs of Resistance against length. You could go on to plot graphs of Resistance against length.

The test wire is attached to a metre rule.

Using a resistance meter

Using batteries, voltmeter and ammeter

Using a power supply, voltmeter and ammeter (1)

Using a power supply, voltmeter and ammeter (2)

Using a resistance meter  Length, l Advantages Easy to set up and read. Easy to set up and read. No problems with the wire getting hot. No problems with the wire getting hot. No need to calculate resistance. No need to calculate resistance. DIsadvantages Maximum grade C. Maximum grade C.

Using batteries, voltmeter and ammeter Length, l A V Advantages The wire shouldn’t get too hot. The wire shouldn’t get too hot. Can achieve up to grade B. Can achieve up to grade B.Disadvantages Maximum grade B. Maximum grade B. 2 meters to read. Resistance has to be calculated 2 meters to read. Resistance has to be calculated No control over current. No control over current. Batteries may go flat. Batteries may go flat.

Using a power supply, voltmeter and ammeter (1) Length, l A V 10  Length, l Advantages The wire shouldn’t get too hot. The wire shouldn’t get too hot. Can achieve up to grade A. Can achieve up to grade A. More control over voltage and current. More control over voltage and current. No batteries to go flat. No batteries to go flat. Disadvantages 2 meters to read. Resistance has to be calculated. 2 meters to read. Resistance has to be calculated. Limited range of voltage and current. Limited range of voltage and current.

Using a power supply, voltmeter and ammeter (2) Length, l A V Advantages Quite esy to set up. Quite esy to set up. Can achieve up to grade A. Can achieve up to grade A. Total control over voltage and current. Total control over voltage and current. No batteries to go flat. No batteries to go flat. Disadvantages The wire could get very hot. The wire could get very hot. 2 meters to read. Resistance has to be calculated. 2 meters to read. Resistance has to be calculated. Some students find the circuit more difficult to understand. Some students find the circuit more difficult to understand.