Question

Two resistors of equal resistance are connected in SERIES to a battery with negligible

internal resistance. The current through the battery is I. When the two resistors are
connected in parallel to the same battery, the current through the battery will be

A. 1/2I
B. I.
C. 2I.
D. 4I.

Answer 1

The correct answer is D (4I). If R is the resistance of one resistor, then IN SERIES circuit total res. will be 2R. If the two res. are in parallel circuit then R(total) = (1/R+1/R)^-1 = (2/R)^-1 = 0.5R. The total res. in the circuit has decreased 4 times (2R/0.5R), so we can deduct that total current has increased 4 times, keeping in mind the Ohm’s law where I=V/R.