A conducting enclosure is used to shield sensitive equipment from an external electrostatic field. Explain the electrostatic-equilibrium mechanism and the limitation of extending that statement without qualification to every time-varying electromagnetic field.

A current-carrying rectangular coil lies in a magnetic field. Explain how magnetic forces can create torque and why opposite sides of the coil experience forces that form a couple.

Two point charges, $q_1 = +3.0 \mu\text{C}$ and $q_2 = -5.0 \mu\text{C}$, are separated by a distance of $0.2 \text{ m}$ in a vacuum. What is the magnitude of the electrostatic force between them? ($k = 8.99 \times 10^9 \text{ N}\cdot\text{m}^2/\text{C}^2$)

Enlarge

A point charge $q = -4.0 \text{ nC}$ is located at the origin. What is the magnitude and direction of the electric field at a point $P$ located $0.5 \text{ m}$ away on the positive x-axis?

Two point charges are located on the y-axis: $q_1 = +2.0 \mu\text{C}$ at $y = 0.3 \text{ m}$, and $q_2 = +2.0 \mu\text{C}$ at $y = -0.3 \text{ m}$. Find the net electric field at point $P$ on the x-axis at $x = 0.4 \text{ m}$.

Enlarge

A $12 \text{ V}$ car battery is connected across a single headlight bulb. A current of $3.0 \text{ A}$ flows through the circuit. What is the resistance of the bulb, and how much power does it dissipate?

Enlarge

A $9 \text{ V}$ battery is connected to a circuit containing three resistors. Resistor $R_1$ ($10 \ \Omega$) is in series with a parallel combination of $R_2$ ($20 \ \Omega$) and $R_3$ ($30 \ \Omega$). What is the total equivalent resistance of the circuit?

Enlarge

Using the circuit from the previous example ($9 \text{ V}$ battery, total $R_{eq} = 22 \ \Omega$), what is the current flowing out of the battery, and what is the voltage drop across $R_1$ ($10 \ \Omega$)?

Enlarge

An electron ($q = -1.6 \times 10^{-19} \text{ C}$) is moving at $5.0 \times 10^6 \text{ m/s}$ due East through a uniform magnetic field of $2.0 \text{ T}$ pointing due North. What is the magnitude and direction of the magnetic force on the electron?

Enlarge

A straight segment of wire $0.5 \text{ m}$ long carries a current of $4.0 \text{ A}$. It is placed in a uniform magnetic field of $0.8 \text{ T}$. If the wire experiences a maximum magnetic force of $1.6 \text{ N}$, what must be the angle between the wire and the magnetic field?

Enlarge

Two long, straight, parallel wires are separated by $0.1 \text{ m}$. Wire A carries a current of $5.0 \text{ A}$ upwards. Wire B carries a current of $8.0 \text{ A}$ downwards. What is the magnitude and direction of the net magnetic field halfway between the two wires? ($\mu_0 = 4\pi \times 10^{-7} \text{ T}\cdot\text{m/A}$)

Enlarge