AP Physics C: E&M Questions on Energy Stored in an Inductor

📚 Quick Study Guide

• ⚡ The energy $U$ stored in an inductor with inductance $L$ carrying a current $I$ is given by: $U = \frac{1}{2}LI^2$.
• 💡 Inductance $L$ depends on the geometry of the inductor (e.g., number of turns, area, length for a solenoid).
• 🧲 Energy is stored in the magnetic field created by the inductor.
• 🔄 When the current changes, the energy stored in the inductor also changes.
• 📝 Power delivered to an inductor is the rate of change of energy with respect to time: $P = \frac{dU}{dt} = LI \frac{dI}{dt}$.

Practice Quiz

1. Question 1: An inductor of 3 H has a current of 2 A flowing through it. What is the energy stored in the inductor?
   1. 1 J
   2. 3 J
   3. 6 J
   4. 12 J
2. Question 2: If the current through a 4 H inductor changes from 0 A to 3 A in 2 seconds, what is the average power delivered to the inductor during this time?
   1. 4.5 W
   2. 9 W
   3. 18 W
   4. 36 W
3. Question 3: An inductor stores 50 J of energy when the current through it is 5 A. What is the inductance of the inductor?
   1. 2 H
   2. 4 H
   3. 8 H
   4. 10 H
4. Question 4: The energy stored in a 2 H inductor is 36 J. What is the current flowing through it?
   1. 3 A
   2. 4 A
   3. 6 A
   4. 9 A
5. Question 5: If the inductance of a coil is doubled and the current is halved, what happens to the energy stored in the inductor?
   1. Energy remains the same.
   2. Energy is doubled.
   3. Energy is halved.
   4. Energy is quadrupled.
6. Question 6: An inductor has an inductance of $L$. If the current through it varies with time as $I(t) = 5t^2$, what is the energy stored in the inductor at time $t = 2$ seconds?
   1. 10L
   2. 25L
   3. 50L
   4. 200L
7. Question 7: A solenoid with inductance $L$ has $N$ turns. If the number of turns is doubled, and all other dimensions remain the same, how does the stored energy change for the same current $I$?
   1. Energy remains the same.
   2. Energy is doubled.
   3. Energy is quadrupled.
   4. Energy is halved.