Question

Assertion(A) : The e.m.f of the cell in secondary circuit must be less than e.m.f of cell in primary circuit in potentiometer.
Reason (R): Balancing length cannot be more than length of potentiometer wire.

• A. Both A & R are true and R is the correct explanation of A
• B. Both A & R are true and R is not a correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer 1

Answer: (A)

When the e.m.f of secondary cell is greater than the primary cell, it implies that the balancing length is greater than the available length. Therefore we cant measure the e.m.f of secondary cell.
$\therefore$ E. M.F of of secondary cell < E.M.F of primary cell.

Hence assertion and reason both are correct and reason is the correct explanation of the assertion.