In the circuit shown in the adjacent figure

Options

A. the potential at `P` is `-7.5V`
B. the potential at `Q` is `-1V`
C. the potential at `R` is zero
D. the potential at `S` is zero

Explanation

The current in the circuit `I=((20-10))/((7.5+.5+1+1))=(10)/(10)=1Amp`
The potential difference across `PS V_(PS)=7.5xx1=7.5V`
The potential difference across `Q R`, `V_(QR)=1xx1=1V`
As point `G` is connected to earth hence potentials of `R` and `S` is zero.
The direction of the current in the circuit is from `P` to `S`, hence point `P` is at higher potential.
`:. V_(p)=7.5V`
similarly `V_(Q)= -1V`