Physics (AS & A Level) · May / June 2017 · Paper 11 · Question 36

A computer is used to detect the change of position of a switch. To detect the change of position, the computer requires a potential difference (p.d.) of 0 V to its input at one switch position and a p.d. of between 5 V and 7 V at the other switch position. For each of the circuits, assume the battery has negligible internal resistance. Which circuit provides an input voltage to the computer that enables it to detect the change of position of the switch?

1. A9 V battery with 1 kΩ and 1 kΩ resistors in series, computer input voltage across the lower 1 kΩ resistor, switch in series with the upper 1 kΩ resistor
2. B9 V battery with 1 kΩ and 2 kΩ resistors in series, computer input voltage across the lower 2 kΩ resistor, switch in series with the upper 1 kΩ resistor
3. C9 V battery with 2 kΩ and 500 Ω resistors in series, computer input voltage across the lower 500 Ω resistor, switch in series with the lower 500 Ω resistor
4. D9 V battery with 500 Ω and 2 kΩ resistors in series, computer input voltage across the lower 2 kΩ resistor, switch in series with the lower 2 kΩ resistor

As printed in the paper