Question
(a) A student changes the current in a filament lamp. She measures the current and the potential difference (p.d.) across the lamp.
Fig. 11.1 is an incomplete circuit diagram.
(i) On Fig. 11.1, complete the unfinished circuit symbols.
(ii) One pair of readings for the lamp is shown in the table.
p.d./ V | current /A |
6.0 | 1.2 |
Calculate the resistance of the filament in the lamp for these readings.
resistance of filament = ……………………………………………………..Ω
(iii) After many hours of use, the filament wire in a lamp becomes thinner.
State the effect, if any, on the resistance of the lamp.
(b) (i) Complete the circuit in Fig. 11.2 to show a battery connected to three lamps arranged in parallel.
(ii) Describe two advantages of connecting these lamps in parallel with the battery.
Answer/Explanation
Answer:
(a) (i) ammeter correct symbol in series with lamp
voltmeter correct symbol in parallel with lamp
lamp correct symbol
(ii) R = V/ I in any form
6 ÷ 1.2
5(Ω)
(iii) (resistance) increases
(b) (i) 3 lamp symbols drawn
(lamps connected) in parallel with battery
(ii) any two from:
• lamps all have 6V or full voltage (across them)
• if one (lamp) breaks, others continue to operate/ little/ no effect on others
• lamps can be switched on and off independently