Resistance of circuits
Method overview
Connect ammeter in series and voltmeter in parallel. Change wire length using a sliding contact, record V and I, calculate R = V/I; also compare resistor combinations in series and parallel.
Apparatus set-up
Diagrampower supply; ammeter; voltmeter; switch; test wire; ruler; crocodile clips; resistors
Independent variable
wire length or resistor arrangement
Dependent variable
current, potential difference and resistance
Control variables
wire material/thickness; temperature; supply; contact quality
Apparatus
power supply; ammeter; voltmeter; switch; test wire; ruler; crocodile clips; resistors
Safety
Use low voltage; wire may become hot; switch off before changing circuit.
Scientific rationale
Longer wire gives more lattice interactions and larger resistance; heating changes resistance; series adds resistance while parallel provides more paths.