Two resistors A A\,A and B B\,B are connected in series with a power supply of emf 40 V and negligible internal resistance. The resistors are made from wire of the same material. The wires have the same length. A A\,A uses wire of diameter 3d 3d\,3d and B B\,B uses wire of diameter ddd.
What is the reading on the voltmeter?
4 V4\text{ V}4 V
10 V10\text{ V}10 V
30 V30\text{ V}30 V
36 V36\text{ V}36 V