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FaradayGenerators/

MotorsInduced Current

Lenz’s Law/ Changing B

Transformers

In 1822, Michael Faraday wrote a goal

in his notebook:

“Convert Magnetism

into Electricity”

A magnetic field can induce a

current.

Electromagnetic Induction

The conductor, which is often a

piece of wire, must be ________ to the magnetic lines of

force

Perpendicular

The direction of the induced current is dependent on the relative motion of

the coil with respect to the magnet.

The Generator Effect

State the 4th RHR… one used for Faraday’s

law.

-Outstretched fingers are magnetic field

-Extended thumb is direction wire moves

-Palm shows direction of current flow

Changes mechanical energy into

electrical energy.

Generator

Coil of wire around a soft iron core to concentrate

magnetic force

Armature

Changes electrical energy into mechanical

energy

Motor

When a generator is connected in a closed circuit; the

current flow is proportional to

the _______

Electromotive Force (EMF)

0.707 times the maximum voltage

Effective Voltage

Even though it is called a force, it is a potential difference and is measured in

volts.

Electromotive Force (EMF)

An induced EMF that resists the applied EMF

Back EMF

The formula for calculating EMF, also state what the

variables are.

vBLv is the velocity

B is the field strength

L is the length of the conductor

A permanent horseshoe magnet is mounted so that the magnetic

field lines are vertical. If a student passes a straight wire between the poles and pulls it

toward herself, the current flow through the wire is from left to right. Which is the N – pole of

the magnet?

The top

3 Ways to increase EMF:

Increase the velocity of the wire

Increase the length of the wire

Increase the magnetic field strength

We will use our ____ RHR

when dealing with Lenz’s law

Second

An induced current always flows in such a direction as to oppose

the motion that induced it.

Lenz’s Law

________ currents are generated to

stop the motion of the metal arm of a

sensitive scale.

Eddy

If a mechanical load is placed on

the motor, slowing it down, the back EMF is ______.

Reduced

The N-pole of a magnet is moved

toward the right end of a coil. The

direction of the induced current is?

Counter clockwise

The varying magnetic flux is carried through the core

to the secondary coil which induces a varying EMF in the secondary

coil. This is called ______________

Mutual Inductance

A step-up transformer increases voltage – the current in the primary

circuit is ______ than that in the secondary.

Greater

Upon what does the ratio of the EMF in the

primary of a transformer to the EMF in the secondary of the transformer depend?

The ratio of number of turns of wire in the primary to the number of turns of wire in

the secondary.

Transformer Formula

Vs/Ns = Vp/Np

Or

Ip/Is = Vs/Ns = Vp/Np

In a transformer, current is inversely

proportional to ______

Voltage

The power produced in the primary coil is

______ to the power produced in the secondary coil.

Equal