5 Electromagnetic Induction Free Online FlashCards

How is magnetic flux through a flat surface calculated?

For a uniform field and flat surface, $\Phi_B=BA\cos\theta$, where $B$ is field strength, $A$ is area, and $\theta$ is the angle between the field and the surface normal.

What does Faraday’s law state for a coil of $N$ turns?

For a coil with $N$ turns, Faraday’s law is $\mathcal{E}=-N\frac{d\Phi_B}{dt}$: changing magnetic flux induces an emf.

How do you find induced current from emf and circuit resistance?

For a closed circuit with resistance $R$, the induced current magnitude is $I=\frac{|\mathcal{E}|}{R}$.

What is self-induction?

Self-induction occurs when a changing current in a coil changes its flux and induces an emf in that same coil.

How does energy change form in an ideal LC circuit?

In an ideal LC circuit, energy shifts continually between the capacitor’s electric field and the inductor’s magnetic field.

When is magnetic flux through a surface greatest or zero?

Flux is greatest when the field is perpendicular to the surface and zero when it is parallel.

What is the SI unit of magnetic flux?

The SI unit of magnetic flux is the weber: $1\,\text{Wb}=1\,\text{T}\cdot\text{m}^2$.

What does Lenz’s law determine about induced current?

Lenz’s law says the induced current’s magnetic field opposes the change in magnetic flux that produced it.

An inward magnetic field through a loop increases. Which way does induced current flow?

It flows counterclockwise, producing a magnetic field out of the page to oppose the increasing inward field.

What three changes can alter magnetic flux through a loop?

Magnetic flux can change if the field strength, loop area, or loop orientation changes.

What emf does an inductor produce when its current changes?

The self-induced emf is $\mathcal{E}_L=-L\frac{dI}{dt}$; it opposes a change in current, so an inductor resists current changes.

What is the SI unit of inductance?

Inductance is measured in henries: $1\,\text{H}=1\,\text{V}\cdot\text{s}/\text{A}$.