PHYSICS · Single correct · CBSE · Physics · Current Electricity · Current Electricity
Problem
Two identical cells, each of emf E, are placed in series with a resistor. In Arrangement 1 both cells have the same orientation; in Arrangement 2 one cell is reversed while the rest of the circuit is unchanged. A student claims, “Because the sum of potential differences around the loop must be zero, reversing one cell will not affect the current.” Which statement best evaluates the student’s claim?
(a) Incorrect, because reversing one cell increases the total internal resistance, which lowers the current even though the net emf is unchanged.
(b) Correct, because the magnitude of each cell’s emf is the same regardless of orientation, so the two cells still supply 2E and the current is unchanged.
(c) Incorrect, because reversing one cell changes the sign of its emf, reducing the net source voltage and therefore the current.
(d) Incorrect, because reversing one cell leaves only one cell’s emf driving the loop, so the current is reduced to half its original value rather than staying the same.