Question 1
Fig. 8.2 shows another circuit. Lamps A and B are identical filament lamps.
Fig. 8.2
The current supplied by the power supply is 0.50 A .
Calculate the resistance of lamp A.
resistance =
Fig. 8.2 shows another circuit. Lamps A and B are identical filament lamps.
Fig. 8.2
The current supplied by the power supply is 0.50 A .
Calculate the resistance of lamp A.
resistance =
960Ω
current in each bulb =0.25 OR R=V / I OR(R=) V / I
resistance =240 / 0.25 OR 1 / 480=1 / R+1 / R
A student determines the resistance of resistor R. She uses a circuit including a voltmeter and an
ammeter.
Which circuit does she use?
D
The electric starter motor in a car is switched on and off using a relay.
The relay consists of a plastic case and two flexible springy strips, X and Y, which are made of soft iron. These iron strips act as the switch when a circuit is connected between the terminals W and Z.
Fig. 7.1 shows \(\mathrm{X
Fig. 7.2 shows the equipment from Fig. 7.1 inside a magnetising coil. The magnetising coil is in series with the 12 V car battery and switch S , which is open.
The power of the starter motor is 1.8 kW and it is also operated by the car battery.
The starter motor circuit is connected between terminals W and Z .
Explain why copper wires with a large cross-sectional area are used for this circuit.
small(er) resistance mentioned
less thermal energy produced or wires do not melt or large current mentioned