Question

If a non ideal cell of emf $E$ and internal resistance $r$ is being discharged, then the terminal voltage $\left(V\right)$ across the cell will be

• A. $V=0$
• B. $V>E$
• C. $V<E$
• D. $V=E$

Answer 1

The correct option is C $V<E$

When the cell is discharging, the current in the circuit flows from the $+ve-$ terminal to the $-ve$ terminal of the battery.
Let $a$ load resistance $R\Omega$ be connected to the cell.


For the above circuit:

Equivalent resistance, $R_{eq}=R+r$

$i=\frac{E}{R+r}$

Now, voltage across terminal of the battery can be calculate as:

$V_A-E+ir=V_B$

$V_A-V_B=E-ir$ or, $V=E-ir$

$\Rightarrow V<E$

Why this question? Tip: The terminal voltage across the cell is maximum and equal to its emf ${}^{\prime }{E}^{\prime }$ in an open circuit. $V_{max}=E$ Concpet: Terminal voltage means, voltage acroos emf as well as internal resistance of the cell combined.