EXAM REVISION ELECTRICTY

What is electricity?

A form of energy generated from moving electrons.

Electricity can be transformed into other forms of energy such as…

light, heat, sound, kinetic sound and a combination.

Electricity can be…

static or current

What is current electricity?

Current electricity is the electricity you get from a battery or power point. They flow through a circuit using the following rules:
- If using a battery, they move from the negative end to the positive end of a battery

- they must lose all of their energy before returning to the start point.

- more electrons take the easy route to the end of the circuit than the difficult route.

What is the path an electron takes called?

An electric circuit, and for the circuit to work it must be complete (have no breaks)

What does each circuit need?

a power source, connecting wires and something to use the electrical energy

What is a short circuit?

If the circuit does not have something to use the energy from the electrons then the energy is given to the wires which may overheat and melt (causing a break in the circuit or a fire). This is called a short circuit and it occurs because of the rule that "electrons must lose all of their energy before they return to the power source"

What is voltage?

Voltage measures the amount of energy available to push charges around a circuit, it is measured in volts (v).

What does a voltmeter measure?

It measures the energy used in a particular section of the circuit. The voltmeter measures the difference in the energy of an electron on each side of a resistor (the voltage drop).

Therefore, the voltmeter has to be connected so that it "hugs" part of the circuit.

In series circuits…

every electron passes through each resistor, a break anywhere in the circuit will affect the entire circuit and voltage is split between all of the resistors.

In parallel circuits…

each electron does not pass through every section of the circuit nor every resistor, a break in the circuit will not affect the whole circuit, the voltage is split between each resistor.

What does current measure?

The amount of charge flowing around a circuit every second.

What is current measured in?

the unit ampere (A) by an ammeter

What does resistance measure?

How difficult it is for the electrons to flow through the wires

What is resistance measured in?

Ohms

High resistance (good insulator) =

difficult for the electrons to flow

Low resistance (good conductor)=

easy for electrons to flow

What does the resistance of a material depend on?

what it’s made of, the length of the wire and the thickness of the wire.

What has more resistance? metal wire vs wood

wood

What has more resistance? thin wire vs thick wire

thin wire

What has more resistance? long wire vs short wire

long wire

The total resistance in a series circuit is given as:

R_T = R₁ + R₂ + R₃..

What is the formula for Ohm’s law?

V=IR
V=VOLTS
I=AMPS
R=RESISTANCE

What is static electricity?

The fact the previously neutral objects are now charged.

When two neutral items rub against each other, a charge can

build up. Electrons move off one surface (leaving it positively charged) and move to the other surface (making it negatively charged)

Can you see static electricity?

No, because you cannot see the movement of electrons between items, however you can sometimes see or feel the discharge of the static electricity.

In most circumstances, the charge usually discharges or "leaks" into the environment until both objects are neutral again. That is, the electrons slowly leave or return to the charged items.

Sometimes we feel or see the discharge. This occurs when electrons rapidly returning to or leaving the charged item. When the item is discharged in this way, the electrons release all of their energy as heat, light, sound and motion. We see this as lightening or may feel it as a "zap" when we touch a metal object such as a car door, or our hair may stand up after going down a slide.