Question

(a) A car has two headlamps, connected in parallel, across a 12V battery. There is one switch in the circuit which controls both lamps.
(i) Complete the circuit diagram in Fig. 9.1 to show how the two lamps and the switch are connected to the battery.

                      Fig. 9.1

(ii) The current passing through each lamp is 4.0A.
The potential difference across each lamp is 12V.
Calculate the resistance of each lamp.
State the unit of your answer.

                                 resistance = …………………….. unit ……………….
(b) The car is crossing a long bridge.
Fig. 9.2 shows a gap in the road surface in the middle of the bridge.

On a hot day the temperature of the road surface increases.
(i) State what happens to the gap as the temperature increases.

…………………………………………………………………………………………………………………….

(ii) Explain why the gap is needed.

……………………………………………………………………………………………………………………
…………………………………………………………………………………………………………………….
(c) The driver of the car notices that the sound from the engine is louder and has a higher pitch when the car accelerates up a hill.
(i) State how the amplitude of the sound wave changes when the car accelerates up the hill.
…………………………………………………………………………………………………………………….
(ii) State how the frequency of the sound wave changes when the car accelerates up the hill.
…………………………………………………………………………………………………………………….

(iii) The car gains thermal energy as it accelerates up the hill.
State two other forms of energy gained by the car as it accelerates up the hill.
1 ……………………………………………………………………………………………………………………
2 ……………………………………………………………………………………………………………………….

▶️Answer/Explanation

Ans:  9(a)(i) all symbols correct ;

two lamps in parallel with battery ;
switch to control both lamps ;

9(a)(ii) R = V/I (in any form symbols or words) or 12/4 ;

      = 3 ;
       ohms / Ω ;

9(b)(i) gap is smaller/closes ; 
9(b)(ii) road/bridge needs to expand on hot day/
road/bridge could be damaged by expansion ;

9(c)(i) amplitude increases ; 
9(c)(ii) frequency increases ;

9(c)(iii) kinetic (energy);

gravitational potential (energy) ;