In the circuit shown

Options

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

Explanation

The current in the circuit`I=(20-10)/(7.5+0.5+1+1)=(10)/(10)=1amp`
The potential difference across PS,` V_(ps) = 7.5 xx 1 = 7.5 V`
The potential difference across Q, R, `V_(QR) = 1 xx 1 = 1 V`
As point G is connected to earth, hence potentials of R and Sare zero. The direction of the current in the circuit is from P to S, hence point P is at higher potential
therefore`V_(p)= 7.5 V`,
Similarly, `V_(Q) = -1 V`
Hence, (B) (C) & (D) are correct.