Electricity and Magnetism

Atomic Review

An atom consists of 3 particles:

Protons-positively chargedNeutrons-no chargeElectrons-negatively

charged

What is Electricity?

• A form of energy caused by moving electrons.

How charges act

Like charges repel Opposites charges attractElectrons flow from a

negatively charged area to a positively charged area

Most objects are electrically neutral

Static Electricity

Phenomena

LightningLeather car seatsBen Franklin and the

kite.Sliding your feet on a rug

How are charges transferred?

When you rub two substances together you do work and thus you add energy.

This removes electrons from one substance and adds it to the other.

This creates IONS which are charged particles.

Summary

The energy used to rub two things together is the

energy that gets involved in removing and

transferring electrons.

Electrical Charge

Can be Transferred.

It cannot be created or destroyed.

Conductors

A conductor allows charges to flow easily

Some conductors are better than others Examples: Copper Iron

Insulators

An insulator prevents electric charges from flowing easily Examples:Rubber CorkWood Plastic

Electric Current

Electric Current is the flow of electrons through a conductor

There are two types of electric current: Alternating Current Direct Current

Alternating Current

Changes direction at a regular rate Most commonly used type of

electricity because it does not create as much heatExamples:Appliances HousesChristmas lights

Direct Current

Always flows in one direction Always flows from negative to

positive

Example:Battery

Creates a lot of heat

What is a Battery?

A series of electrochemical cells Two types:

A wet cellA dry cell

Wet cell

Electrolyte is a liquid Example:Car battery

Dry cell

Electrolyte is a moist pasteExample:AA battery

What is a circuit?

The path an electric current follows Consists of four parts:

Source Load

Wires Switch

Current flows only through a closed circuit

Diagrams

Source Resistance

Lamp Motor

Wire

Switch

What is a series circuit?

A circuit where current follows only one path

If one light goes out, the whole circuit goes out

Diagram of a Series Circuit

What is a parallel circuit?

Current follows more than one path If one light goes out, the others

remain on. Used in:

HomesSchoolsBuildings

Diagram of a Parallel Circuit

Circuit diagrams are a pictorial way of showing circuits. Electricians and engineers draw circuit diagrams to

help them design the actual circuits. Here is an example of a

circuit.                                                                           

What are volts? Electromotive force (EMF) is the force

that moves electrons in a circuit. A volt is the unit used to measure EMF.

What are amps?

The amount of current depends on the number of electrons flowing in the circuit.

An ampere (amp) is the unit used to measure current.

What are ohms?

Resistance opposes the flow of electrons in a circuit.

Resistance of a wire depends on length, thickness, material, and temperature.

An ohm is the unit used to measure resistance.

Magnetism

Where do magnets come from?

Earth is a magnetIron can be made into magnets

3 things stick to magnets iron, nickel, cobalt

Magnetic Pole

A pole is the area of the magnet where the magnetic effect is the strongest.

One pole of the magnet will always point north this is the north pole.

The south pole will point south. The north and south poles are

unlike and therefore attract.

Magnetism

MagneticFields

Magnetic Fields

Exist in regions surrounding magnets.

Exerts a torque on a compass needle. (Demo)

Compass needles allow us to map out magnetic fields.

Magnetic field lines flow out of the north pole and into the south pole.

They are continuous and never cross

The Earth itself is a magnet!

Earth’s magnetic field causes compasses to line up.

Magnetic north/south pole is about 11º off from geographic north/south pole.

Why?

Scientists are not sure why the Earth is a giant magnet but some believe that it is due to the circulation of molten metal (iron and nickel) within the Earth’s core.

Oersted’s Discovery!

The presence of an electric current in a wire causes a torque in a compass nearby.

A current carrying wire generates a magnetic field.

Electromagnetism.

Electric Current

The flow of charge through a material

The amount of charge that passes through the wire in a unit of time is the rate at which the

electric current flows. The unit of current is the ampere or amp.

An electric current produces a magnetic field.

The direction of the current determines the direction of the magnetic field in a current carrying wire.

Cause

All magnetism is caused by the movement of charges.

Electromagnet

An electromagnet is a strong magnet that can be turned on and off.

Increase strength

Increase the strength of a magnet by: Increasing the current Increasing the number of loops of

wire to the solenoid. Wind the coils of a solenoid closer

together. Use stronger ferromagnetic material

for the core.