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who first demonstrated the principle of electromagnetic induction

### Electromagnetic induction

producing current in a wire by placing it in a changing magnetic field

### wire&wire

Either the ____ can move in the magnetic field or the field can move around the ____ - one or the other must move to induce current.

### -rotate a wire -drag a wire through magnetic field -move a magnetic field across a wire

three ways to induce current

### emf

Separation of charges by magnetic force will induce ____in the wire

### electrons

The magnetic field force pushes the___ through the wire

### 3rd

Use the ___ right hand rule to figure out the direction of current flow in the wire

### -speed of wire or magnetic field motion -length of wire in the field -strength of magnetic field

Magnitude of emf depends on (3):

### perpendicular

Induced current is greatest if the wire and magnetic field are_____ to each other

### parallel

if the angle is zero the wire is____ to the magnetic field

### perpendicular

Only the portion of the magnetic field____ to the wire will induce current in it

### size & rotating

Changing the ___ of the loops of wire or _____ the loop in the magnetic field will change the amount of induced current

### magnetic field

The current induced in the wire by moving through a magnetic field will generate its own _______

### opposite

As the magnetic field approaches the wire, the wire's magnetic field is in the____ direction of the increasing magnetic field

### bar magnet

The induced magnetic field is similar to a _____- and creates a force that repels the original magnetic field

### same

As the coil moves out of the magnetic field the induced field is in the_____ direction as the original and they attract each other

### lens law

"The magnetic field of an induced current is in a direction to produce a field that oppose the change causing it"

### CHANGE

The induced field does not oppose applied field, but the____ in the applied field

### induced field

If the applied field changes, the _____ helps to keep it constant

Predicts the magnitude of induced emf

### Lenz's law

tells the direction of the induced emf

### Equation for single loop

emf = -∆ϕM/∆t

### emf from one loop

When you have multiple loops, you multiple the number of loops (N) by the ____

N∆ϕM/∆t

### volt (V)

emf unit is the

### orientation

Current can also be generated in a magnetic field by changing the_____ of the loop in the magnetic field

### mechanical energy

Most power plants use a source of _____ to turn a turbine in a magnetic field to generate current.

### emf

A generator produces changing____, because of its constant rotating

### 0 emf

when the armature is perpendicular to the magnetic field in a generator, you get____

### maximum emf

when the armature is parallel to the magnetic field in a generator, you get ____

### AC current

As the loop rotates from one arm being up to the other being up, the current flow will change direction - producing ____

emf = NAβω

### ω

is the angular speed of rotation of the loop (2πf)

### frequency

The____ of rotation of the loop in a generator will determine how often the current changes direction -> f = 60Hz in US

### AC can be converted to DC

add rings (slip rings) and brushes to the end of the loops, the moving rings counter the changing current and create direct current for a circuit

### motor

convert electrical energy to mechanical energy

### permanent magnet

Current is supplied to loops and that magnetic field repels ______ and causes the loops to rotate

### back emf

The motor's magnetic field generates its own emf called ___

### Back emf

____ increases as the magnitude of the magnetic field changes at a higher rate

### potential difference

The _____ supplied to the motor equals the applied emf minus the back emf, this also reduces current

### reduce

As a motor turns more quickly, the net emf and net current in the coil___

### Mutual inductance

____ is the ability of one circuit to induce emf in a nearby circuit in the presence of a changing magnetic field

### Mutual inductance

emf = - M(∆I/∆t)

### M

__ depends on the shape of the coils and how they are orientated to each other

### M

is the mutual inductance of the two-coil system

### number

Changing the____ of coils in the secondary coil can change the induced emf in the secondary coil - used in making transformers

### emf & current

Because AC current changes direction, the____ and____ in an AC circuit is not constant

### emf & current

Effective ___ and effective ____ are the average values in the AC circuit - called Irms

### Ohm's Law

You can use ____ to find resistance

### transformers

A device that increases or decreases the emf of alternating current

### first coil called primary

current in this coil magnetizes the iron core

### Second coil called secondary

current runs through the 2nd coil because it is wrapped around magnetized iron

### Real transformers

_____ are only 90-99% efficient - power is lost due to small currents induced by changing magnetic field and resistance in the wires

### transformer equation

∆V2/∆V1 = N2/N1

### Step-up transformer

increases the emf, N2 is greater than N1

### Step-down transformer

decreases the emf, N2is less than N1

### decrease

The increase in emf means a____ in current

### increase

An decrease in emf means an____ in current

### 230 000V

In the US, power companies step-up emf to about ____

### 12V

Car batteries provide a constant DC emf of ___

### The Ignition coil

____ in the engine is a transformer that increases this emf to a great enough value to cause a spark between the gaps of a spark plug

### electromagnetic waves

Oscillating electric and magnetic fields create

### James Clerk Maxwell

____created a set of equations that explain the relationship between electric and magnetic fields

### electromagnetic in nature

Maxwell predicted that light was ___-

### Heinrich Hertz

___performed experiments that generated and detected EM waves and confirmed Maxwell's predictions.

### transverse waves

electromagnetic waves are ___

### right

Oscillating Electric and Magnetic waves - at___ angles to each other

### single force

Electric and magnetic forces are aspects of a ____ - called electromagnetic force

### inverse square law

Electromagnetic force obeys the ____ - as the two objects move further apart the force between them weakens

### accelerating charges

All EM waves are produced by ____ - a charge moves up/down through the wave at a certain frequency

### charged particular

motion of _____ through a wave makes it move

### energy

Electromagnetic waves transfer____ - stored in the oscillations of the electric and magnetic fields

Energy transported by EM waves is called ____

### particles

Some high energy EM waves will behave like____

### wave-particle duality of light

Notion that EM waves behave like particles is called the____

### photon

A particle of light is called a____ - carries energy, but has no mass

### waves

Low-energy photons behave more like ___

### particles

High-energy photons behave more like____

Example: