A2L Item 250
- Description: Identify the total energy dissipated in a resistor as an L-R circuit reaches maximum current.
- Goal: Reason regarding RL circuits.
- Source: 283 - energy dissipated in inductor
- Keywords: Inductors, Energy, Electromagnetism, Circuits, Resistance
The question for students:
Consider the following circuit. The switch S is closed at t = 0. The total energy dissipated in the resistor before the current reaches its maximum value is:
- V^2^/2R
- LV^2^/2R2
- LV
- V/RL
- none of the above
Commentary for teachers:
Answer
(5) The total work done by the battery is QV where Q is a function of time which is not limited. The total energy stored in the inductor is finite. The difference must be the energy dissipated in the resistor. Since it takes an infinite amount of time for the current to reach its maximum value, the total amount of energy dissipated is also maximum.
A good follow up question is: Is there a time when the dissipated energy is equal to the stored energy? If so, what is that time?