ELECTRICITY

Static Electricity• Static electricity is when a charge

is built up on an object. The charges do not move. This is usually caused by friction. Examples: feet rubbing against the carpet, combing hair, rubbing a plastic strip with a cloth.

Static Electricity• Static electricity

cannot hurt.• Static electricity

does not supply any useful energy.

There are 3 types of charges.• Positive• Negative• Neutral – This

means that there is no net charge on the object. There are equal numbers of + and – charges.

• Opposite charges will attract.

• Like charges will repel.

• Neutrally charged objects are attracted by both + & -.

• This is a very strong force.

Conductors and Insulators• A conductor is a

substance that allows current to flow through it.

• Examples: copper & most other metals, graphite, the human body

• An insulator is a substance that does not allow current to pass through it easily.

• Examples: plastic, rubber, glass, wood.

Current Electricity• Current is when the charges are

moving. The movement allows them to do work for us. Examples: lightning, a “shock” from a door knob, current in a wire

Current• Current can cause

pain and/or be fatal. Care is required.

• Current also supplies a great deal of useful energy.

Characteristics of Current

Voltage• The amount of energy carried by the

electrons moving through the circuit.• Measured in volts (v)• 1 volt = 1 joule per coulomb of

charge• The voltage is set by the energy

source. Example: a 1.5 volt battery or a 110 volt wall socket

Current• The flow of electrons through a

conductor.• Measured in amperes (amps)• 1 amp = 1 coulomb per second• Set by the appliance.

Resistance• The tendency of a

material to resist the flow of charges.

• Measured in ohms ()• The filament in a light

bulb has a high resistance. This is why it gets so hot it glows.

Series and Parallel Circuits

Series Circuits• In a series circuit

all the current must flow through every appliance in the circuit. If one of the appliances goes out, they all go out. Notice that the energy seems to run out.

Series Circuit

Parallel Circuit• In a parallel

circuit the current flow splits up and goes to different parts of the circuit. If one bulb or appliance goes out, the rest stay on. All bulbs are equally bright.

Parallel Circuit

Schematic DiagramsSeries Circuit

Parallel Circuit

Direct Current (DC) & Alternating Current (AC)

Direct Current• Direct current is

when the electrical current moves in one direction all the time.

• Examples: batteries

Alternating Current• Alternating current

is when the direction of the flow of current changes 60 times per second. It can be carried long distances from power plants

• Example: wall sockets

Power• The amount of energy used in a period

of time; P = energy / time• For electricity: Power = voltage x

current (P = v x i)

• Units: watts or kilowatts (1000 watts)

Energy• The ability to do work

or cause change.• For electricity: Energy

= voltage x current x time (EE = v x i x t) or (EE = P x t)

• Units: joules or kilowatt-hours