Question

Question #c3b78

Answer 1

I would go for B) zero to `7.5V`

Explanation:

The variable resistor can be set (I think) starting at zero up to `50kOmega`.

At zero (basically the resistor becomes a simple wire) the voltage drop between points P and Q is zero (or the difference in potential between them is zero).

When at `50kOmega` we can use Ohm`s Law:
`V=Ri`
to find the current in the circuit comprising the series of the two resistors:
`i=V/R=9/(10kOmega+50kOmega)=1.5xx10^-4A`
and again to find the voltage drop across the variable resistor (at `50kOmega`):
`V_(PQ)=50kOmega*1.5xx10^-4A=7.5V`