# Electromagnetic Induction & Inductance

An electric field is induced in any region of space in which a magnetic field is changing with time.

Lenz's Law

The direction of the induced EMF drives current around a wire loop to always oppose the change in magnetic flux that causes the EMF

what does the magnetic flux depend on?

magnitude of magnetic field, area, orientation of the field

Faraday's Law holds for all flux changes, whether they are produced by a changing magnetic field, by motion, or a combination of the two (T/F)

Ture, Faraday's law holds for all flux changes

the power dissipated in the circuit by the emf

motional emf

The emf produced across a conductor due to its motion through a magnetic field

eddy currents

these produce significant drag called magnetic dampening on the motion

in which direction does the eddy current face in terms of the velocity vector?

they are parallel to each other but in opposite directions

A flat, circular, copper loop of radius r is at rest in a uniform magnetic field of magnitude B that extends far beyond the edge of the loop. The plane of the loop is parallel to the page and the magnetic field is directed perpendicular to and out of the

The induced current is constant and flows clockwise around the copper loop.

A very long, straight wire carries a steady current, I, to the left, as shown in the figure. Near the wire, but not touching it, is a circular copper-wire loop that is oriented with its plane parallel to the page. If the circular loop is pulled away from

The induced current in the circular loop flows counterclockwise.

A rectangular wire loop is pulled out of a region of uniform magnetic field B at a constant speed v. What is true about the induced emf in the loop while the loop is pulled out of the region of uniform magnetic field?

There is a constant emf induced in the loop

A rectangular wire loop is pulled out of a region of uniform magnetic field B at a constant speed v. What is true about the magnetic flux through the loop while the loop is pulled out of the region of uniform magnetic field?

The magnetic flux through the loop decreases at a constant rate as the loop is moved to the right.

A bar magnet is dropped above the center of a circular metal loop such that the magnet falls through the center of the loop. What is true about the acceleration of the magnet as it falls through the loop?

The magnet falls with an acceleration that is less than g.

A very long, straight wire carries a steady current, I, to the left. Near the wire, but not touching it, is a circular copper-wire loop that is oriented with its plane parallel to the page. If the circular loop is pulled to the right along the direction o

There is no induced current in the circular loop.

inductance

the property of a device that tells you how effectively it induces an emf in another device

mutually inductance

when two circuits carrying time-varying currents are close to one another, the magnetic flux through each circuit varies because of the changing current in the other circuit, therefore an emf is induced

Mutual inductance can depend upon

the relative position of the two circuits and their shape

mutual inductance is dependent upon the currents through each circuit (T/F)

False

describe the relationship between the magnetic flux and current

they share a directly proportional relationship

when do current and magnetic flux NOT have a directly proportional relationship?

when self-inductance is present

self-inductance

The induction of EMF in a wire carrying a changing current

in which way does the induced current travel along the wire?

it travels opposite to the direction of the flowing electrons (original current)

inductor

a circuit element with the property of self-inductance

inductors have the capability to store ____________________ in their magnetic field

energy

what quantities does the potential energy stored by an inductor depend on?

self-inductance & current

RL circuit

A circuit that contains resistance and inductance

inductive time constant

When an inductor is connected in series with a resistor and DC source, the current increases exponentially from zero to its maximum value and the voltage across the inductor decreases exponentially from max value to zero

LC circuit

an idealized circuit with zero resistance that contains an inductor and a capacitor

What is the effect of inductance on a RL series circuit?

As the change of current increases so does the emf. The current will continue to rise but at a slower rate of change, therefore the emf decreases. This is until the current reaches it maximum steady state and then there is no emf.

series inductance

parallel inductance

in a LC circuit what happens after the capacitor is completely discharged?

the current reaches a maximum

the maximum energy stored in the capacitor of a LC circuit is the same as _________________

the maximum energy in the inductor

the current value and the magnetic flux always change at the same _______________

frequency

A vertical bar magnet is dropped through the center of a horizontal loop of wire, with its north pole leading. At the instant when the midpoint of the magnet is in the plane of the loop, the induced current at point P, viewed from above, is:
A. maximum an

E. essentially zero

A circular loop of wire is positioned half in and half out of a square region of constant uniform magnetic field directed into the page, as shown. To induce a clockwise current in this loop:
A. move it in +x direction
B. move it in +y direction
C. move it

A. move in the +x direction

A rod lies across frictionless rails in a constant uniform magnetic field B The rod moves to the right with speed v. In order for the emf around the circuit to be zero, the magnitude of the magnetic field should:
A. not change
B. increase linearly with ti

C. decrease linearly with time

A rectangular loop of wire is placed perpendicular to a uniform magnetic field and then spun around one of its sides at frequency f. The induced emf is a maximum when:
A. the flux is zero
B. the flux is a maximum
C. the flux is half its maximum value
D. t

A. the flux is zero