electricity, magnetism and electromagnetism

ELECTRICITY, MAGNETISM AND

ELECTROMAGNETISM.

ATOMS…

Have neutrons, protons, and electrons.

Protons are positively charged

Electrons are negatively charged

ELECTRONS…

Are located on the outer edges of

atoms…they can be moved.

A concentration of electrons in an atom

creates a net negative charge.

If electrons are stripped away, the atom

becomes positively charged.

+-

+

+

++

THE WORLD IS FILLED WITH ELECTRICAL

CHARGES:

+

+

+

+

+

-

-- -

-

-

- --

STATIC ELECTRICITY

The build up of an electric charge on the surface of an object.

The charge builds up but does not flow.

Static electricity is potential energy. It does not move. It is stored.

STATIC DISCHARGE…

Occurs when there is a loss of static

electricity due to three possible things:

Friction - rubbing

Conduction – direct contact

Induction – through an electrical field

(not direct contact)

ELECTRICITY THAT MOVES…

Current: The flow of electrons from one

place to another.

Measured in amperes (amps)

Kinetic energy

HOW CAN WE CONTROL CURRENTS?

With circuits.

Circuit: is a path for the flow of electrons.

We use wires.

Static electricity is stationary or collects on the surface of

an object, whereas current electricity is flowing very

rapidly through a conductor.

The flow of electricity in current electricity has

electrical pressure or voltage. Electric

charges flow from an area of high voltage to

an area of low voltage.

Water pressure and voltage behave in

similar ways.

THERE ARE 2 TYPES OF CURRENTS:

Direct Current (DC) – Where electrons

flow in the same direction in a wire.

THERE ARE 2 TYPES OF CURRENTS:

Alternating Current (AC) – electrons

flow in different directions in a wire

THERE ARE 2 TYPES OF CIRCUITS:

Series Circuit: the components are lined

up along one path. If the circuit is

broken, all components turn off.

SERIES CIRCUIT

THERE ARE 2 TYPES OF CIRCUITS:

Parallel Circuit – there are several

branching paths to the components. If

the circuit is broken at any one branch,

only the components on that branch will

turn off.

PARALLEL CIRCUIT

CONDUCTORS VS. INSULATORS

Conductors – material through which

electric current flows easily.

Insulators – materials through which

electric current cannot move.

EXAMPLES

Conductors:

Metal

Water

Insulators:

Rubber

Plastic

Paper

WHAT IS RESISTANCE?

The opposition to the flow of an electric current, producing heat.

The greater the resistance, the less current gets through.

Good conductors have low resistance.

Measured in ohms.

WHAT IS VOLTAGE?

The measure of energy given to the

charge flowing in a circuit.

The greater the voltage, the greater the

force or “pressure” that drives the

charge through the circuit.

OHM’S LAW

Resistance = Voltage / Current

Ohms = Volts / Amps

V= IR I =V/R R=V/I

MAGNETISM

What is magnetism?Magnetism is the properties and interactions of magnets

The earliest magnets were found naturally in the mineral magnetite which is abundant the rock-type lodestone. These magnets were used by the ancient peoples as compasses to guide sailing vessels.

Magnets produce magnetic forces and have

magnetic field lines

The earth is like a giant magnet!

The nickel iron core of the earth gives the earth a

magnetic field much like a bar magnet.

MAGNETS

USUALLY MADE OF IRON

EVERY MAGNET HAS A NORTH AND SOUTH

POLES

LIKE SIMILAR CHARGES REPEL

OPPOSITES ATTRACT

FERROMAGNETIC

OBJECTS THAT CAN BE MAGNETIZED

(IRON, COBALT, NICKEL)

3 TYPES OF MAGNETS

LODESTONE – NATURAL (PERMANENT)

ARTIFICAL – INDUCED

ELECTROMAGNET – temporary magnets

produced by moving electric current

Ferromagnetic

material such as iron

attracts magnetic

lines of induction,

whereas nonmagnetic

material such as

copper does not.

Demonstration of

magnetic lines of

force with iron filings

NORTH &

SOUTH POLES

If a single magnet is

broken into smaller

and smaller pieces,

baby magnets result

A moving charge creates a magnetic field

When a charged particle is in motion – a magnetic force field perpendicular to the motion is created

ELECTROMAGNETISM

ELECTROMAGNETISM

A MOVING CHARGE CREATES A MAGNETIC

FIELD

RT HAND RULE

Current flow direction of thumb

–

Magnetic filed – fingers

ELECTROMAGNET IS CREATED BY:

SOLENOID: Current flowing

through coil of wire

Putting a magnet in the

middle of the coil of wire

increases the strength of the

electromagnet’s magnetic

field

A coil of wire is a helix

Supplied with current it is a solenoid

Add an iron core – simple form of

ELECTROMAGNET

What is an electromagnet?

When an electric current is passed through a coil of wire

wrapped around a metal core, a very strong magnetic

field is produced. This is called an electromagnet.

HOW ELECTRIC & MAGNETIC FIELDS

INTERACT

Faraday discovered that the

magnetic lines of force and the wire

must have a motion relative to each

other to induce an electrical current

ELECTROMAGNET INDUCTION

Moving a wire through a magnetic field

will induce a current (Faraday)

Wire or field can move

Moving a magnet through a coil of wire

will induce an electrical current

“FARADAY’S LAWS : OR HOW TO INCREASE THE

STRENGTH OF THE INDUCED CURRENT

Increase the Strength of field or size of

magnet

Increase the SPEED of motion

Change the ANGLE (more

perpendicular)

Increase the Number of Turns of coil

ELECTROMAGNET INDUCTION

MOVING A BAR

MAGNET THROUGH A

COIL OF WIRE WILL

INDUCE A CURRENT

TO FLOW THROUGH

THAT WIRE

What are electric motors?An electric motor is a device which changes electrical

energy into mechanical energy.

How does an electric motor work?

THE PRINCIPLE OF THE ELECTRIC MOTOR

GENERATORS

A generator is a device that uses induction to convert mechanical energy into electrical energy.

TRANSFORMERS

A transformer is a device used to change the

voltage in a circuit. AC currents must be used.

75,000 V in the

power lines

120 V in your

housep = primary

s = secondary

Transformers are extremely useful because they efficiently change voltage and current, while providing the same total power.

The transformer uses electromagnetic induction, similar to a generator.