Question

Find the potential difference between the points P and Q in the given circuit?

• A. 3.25V
• B. 3.5V
• C. 3V
• D. 3.75V

Answer 1

The correct option is A 3.25V

Cells are in parallel. We can use a direct formula. For two cells in parallel, we can apply
$E=\frac{E_1{r}_2+E_2{r}_1}{r_1+r_2}r=\frac{r_2{r}_1}{r_1+r_2}$
Let’s apply this formula for one pair of rows. And the result we get will be parallel to the second row. So apply it again.
$E=\frac{5\times 1+4\times 1}{1+1}E=4.5Vr=\frac{1}{1+1}=1\Omega$
Now apply this resulting equivalent cell with the third row.
$E=\frac{4.5\times 1+2\times 1}{1+1}E=3.25Vr=1\Omega$
The potential difference between P and Q will be this cell’s voltage.