Faraday Generators/ Motors Induced Current Lenz’s Law/ Changing B Transformers 1pt 1 pt 1 pt 1pt 1 pt 2 pt 2 pt 2pt 2pt 2 pt 3 pt 3 pt 3 pt 3 pt 3 pt 4 pt 4 pt 4pt 4 pt 4pt 5pt 5 pt 5 pt 5 pt 5 pt

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.

L is the length of the conductor vBL v 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 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