Electrical Energy &Magnetism

Electricity Intro: 22min

Electrical Energy

• Energy produced by moving electric charges.– Charges can be positive (+) or negative (-), Ions• Caused by the gain or loss of electrons from the orbits

of an atom.

• Atoms are made of: – Neutrons, in the nucleus, neutral (0)– Protons, in the nucleus, positive (+)– Electrons, on the orbits, negative (-)

Ions• Atoms have equal numbers

of protons & electrons, electrically neutral.– Protons are stationary, don’t

move.– Electrons are free to move.

• Loss of e- = positively charged atom– More protons than electrons

• Gain of e- = negatively charged– Fewer protons than electrons.

Gains Outer

Electron

Positive Ion

Negative Ion

P=11e-=11

P=11e-=11

P=11e-=10

P=11e-=12

Electric Forces• The difference between the two charges, +

and -, causes them to have different forces:1. Force of attraction – force between oppositely

charged particles. (+/-)2. Force of repulsion – force between particles of

the same charge. (+/+ or -/-)

Rule of Electric Charge:

Like charges repel,

opposite charges attract!

Electric Fields

• A field that extends outward through space from every charged particle.– Field is strongest, closest to the charged particle.– Field is weakest, farther from the charged

particle.

Conduction

• The flow of electrons from one object to another through direct contact.– Conductors permit the flow of electric charges freely.

• Electrons in the atoms are free to move.– Metals; silver, copper, aluminum, and mercury.

– Insulators do not allow electric charges to flow freely.• Electrons are tightly bound and cannot move throughout

the material.– Rubber, glass, wood, plastic, air, feathers.

Item Light Bulb Light? Insulator/Conductor

Wood

Copper

Glass

Steel

No

No

Yes

Yes

Insulator

Insulator

Conductor

Conductor

Circuits• In order for electricity to flow, electrons need a closed path

to travel through – circuit.• Parts of a Circuit:

– Energy source• Battery or Electric Outlet

– A load, or resistance• Light Bulb

– Wires– Switch

• Opens and closes the flow of electricity through the circuit.

SwitchEnergySource

WiresLoad

Types of Circuits1. Series Circuit – all the parts of the circuit are

connected one after another.– Only one path for electrons to travel.• From positive to negative

– Disadvantage: A break in any part of the circuit stops all flow of electrons.• Christmas tree lights

+ -

Types of Circuits

2. Parallel Circuits– Different parts of an electric circuit are on

separate branches.• Several paths for electrons to travel.• Advantage: A break in path will not take out the entire

circuit.– Household Circuits

Lodestone

• 2000 years ago, Greeks living in Magnesia discovered a rock with an unusual trait, it attracted materials that contain iron.– Named the rock magnetite.• When allowed to swing freely, the same end of the rock

would always point toward the north star, (leading star or lodestar)– Magnetite is also known as lodestone.

Magnetism

• An invisible force of attraction or repulsion, of a magnetic material, due to the arrangement of its atoms.– Electrons in their outer orbits are in constant

motion and spin causing a magnetic field.• When the electrons all point in the same direction, its

said to have magnetic domain.

Magnetic Domain

• Metals = Magnetic Domain– Electrons all point in the

same direction

• Nonmetals = No magnetic Domain– Electrons have random

arrangements.

Magnets• All magnets have two ends where magnetic

effects are strongest – poles.– North and South

• Have magnetic forces - lines of force extending from one pole of a magnet to the other.– It is the area over which the magnetic force is exerted.

• Magnetic forces always move from the north pole of a magnet to the south pole.– strongest at the poles.

Magnetic Forces

Magnetic Forces

• Just like electric forces, magnetic forces follow the same rule: Opposites attract, like repels.

OppositesAttract

LikeRepels