Paper 1 · November 2002 · Current Electricity
The diagram shows a potential divider which is used to give outputs of 3V and 6V from a 15V source. What are the correct values of resistors?
AR1=1, R2=3, R3=1 (kΩ)
BR1=3, R2=1, R3=1 (kΩ)
CR1=2, R2=2, R3=1 (kΩ)
DR1=1, R2=2, R3=2 (kΩ)
Explanation
Total 15V across R1+R2+R3. 6V node is between R1 and R2, so voltage across R2+R3 = 6V. 3V node is between R2 and R3, so voltage across R3 = 3V. Voltage is proportional to resistance in series. R3:R2:R1 ratio for drops of 3:3:9 → R3=1, R2=1, R1=3. Answer B.
ZIMSEC Physics Paper 1, November 2002, Q14