Question

Vinita and Ahmed demonstrated a circuit that operates the two headlights and the two sidelights of a car, in their school exhibition. 

Based on their demonstrated circuit, answer the following questions. 

(i) State what happens when switch A is connected to 

a) Position 2 

b) Position 3 

(ii) Find the potential difference across each lamp when lit. 

(iii) Calculate the current

a) in each 12 Ω lamp when lit. 

b) In each 4 Ω lamp when lit.

(iv) Show, with calculations, which type of lamp, 4.0 Ω or 12 Ω, has the higher power.

Answer 1

(i) 12 Ω lamps (only) on. 

(a) 4 Ω lamps (only) on

(ii) 12 V for both sets of lamps and all of them are in parallel.

(iii) 12 Ω lamps are on when the wire is connected to position 2.

Voltage across both 12 Ω lamps = 12 V. 

V = IR (Ohm’s law).

4 Ω lamps are on when the wire is connected to position 3. 

Voltage across both 4 Ω lamps = 12 V. 

V = IR (Ohm’s law).

(iv) P = V²/R 

All lamps are in parallel and hence same V for all lamps.

Hence 4 Ω lamps will have higher power.