Question

The diagram shows a simple circuit.
Which statement is correct?

• A. When switch S is closed, the e.m.f. of the battery falls because work is done against the
  internal resistance of the battery.
• B. When switch S is closed, the e.m.f. of the battery falls because work is done against the
  resistance of R.
• C. When switch S is closed, the potential difference across the battery falls because work is
  done against the internal resistance of the battery
• D. When switch S is closed, the potential difference across the battery falls because work is
  done against the resistance of R.

Answer 1

Answer: (C)

When switch S is closed, the potential difference across the battery falls because work is

done against the internal resistance of the battery
The emf of battery never changes in any case. Only the potential drop across the battery changes due to current flowing through its internal resistance.

So, all the options except option C is incorrect.