Multiple choice

In the following figure, C1 and C2 are ideal capacitors. C1 has been charged to 12 V before the ideal switch S is closed at t = 0. The current i(t) for all t is

  1. zero

  2. a step function

  3. an exponentially decaying function

  4. an impulse function

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

When two ideal capacitors are suddenly connected by closing a switch, charge redistribishes almost instantaneously. This produces an impulse (Dirac delta) current at the switching instant t=0, after which the current is zero as the capacitors reach a new equilibrium. The impulse represents the theoretically infinite current that would flow for an infinitesimal time to equalize voltages.

Keep practicing — related questions