Thank you for reporting, we will resolve it shortly
Q.
10 identical cells each of emf E and internal resistance r, are connected in series to form a closed circuit. An ideal voltmeter connected across 3 cells will read:
10 identical cells connected in series.
Potential of each cell $=E$
Internal resistance of each cell $=r$
Total voltage of ten cells $=10 E$
Total resistance of ten cells $=10 r$
Current in the circuit, $I=\frac{10 E}{10 r}=\frac{E}{r}$
Potentiol difference across 3 cells, $V=I \times 3 r$
$
=\frac{E}{2} \times 3 r
$
$
=3 E
$
Hence, ideal voltmeter will read $3 E$.