This experiment looks at the relationship between current and
potential difference (p.d.) for a length of resistance wire.
Apparatus and materials Ammeter (1 amp), DC Voltmeter (5 volt),
DC Eureka wire (34 SWG), 10-cm length Power supply, low voltage,
DC Leads, 4 mm, 6 Crocodile clips, 2 Rheostat (10 ohms, at least
1A) Health & Safety and Technical notes Low voltage power
supplies are not continuously variable. Many have nominal
voltages of 1, 2, 4, 6 etc. In this case the current could be 1,
2, 4, 6 A since 10 cm of SWG 34 Eureka is about 1 Ω. a Set up
the circuit shown. The length of Eureka wire acts as the
resistance in the circuit. b By adjusting the power supply, you
can vary the p.d. across the Eureka wire. The ammeter will show
corresponding values of the current through the wire. Keep the
current small so that the temperature of the wire does not
increase. (Adjust the rheostat at the beginning and then keep it
constant.) Record a series of values of p.d. and current. c
Calculate the ratio p.d./current