Electricity

Cell

Required to push electrons around a circuit

Battery

Something that consists of two or more cells

Wire

Wires should always be drawn as straight lines

Indicator / filament bulb

Often a light bulb - this is used to show whether or not a circuit is on

Light bulb

Old symbol - the indicator symbol is now used

Ammeter

Measures electric current in amperes

Voltmeter

Measures voltage in volts

Fixed resistor

Used to limit the current in a circuit

Thermistor

A device whose resistance decreases with temperature

Diode

Only allows current to flow in one direction

Light emitting diode (LED)

A diode that emits light when it allows the flow of electric current

Fuse

Designed to melt and so break an electric circuit when too much electric current flows

Heater

A device used to convert electric energy to heat

What is an electrical conductor?

A material through which electric current flows easily. All metals are conductors.

What is an electrical insulator?

They have a very high resistance to the flow of electric cuurent.

What is the charge in an atom?

An electron has a negtive charge that is of the same size as the positive charge of a proton. Neutrons have no electric charge

When does current flow?

An electric current of one ampere (A) flows when a charge of one coulomb (C) passes a point in an electric cicuit in one second.

What is the equation for electric charge?

Q = it

What is the equation for electrical power?

P = iv

What is direct current?

Cells and batteries supply electric current in the same direction

What is alternating current?

One which is constantly changing direction

What are most fuses at?

1A, 3A, 5A and 13A

V = ?

V = ir

P = ? in terms of r and i

P = i²r

P = ? in terms of r and v

P = v²/r

What is a circuit breaker?

An electromagnetic device that breaks a circuit when the current goes above a certain value

What are some benefits of a fuse?

Cheap, small to put in a plug

What are some cons of a fuse?

Takes longer than a circuit breaker to break a circuit

What are some benefits of a circuit breaker?

Fast to break the circuit, can be used more than once

What are some cons of a circuit breaker?

Expensive and big so cannot be put in a plug

What is double insulation?

Many electrical appliances have casings made from an insulator such as plastic rather than metal. The electrical parts of the device cannot therefore be touched by the user.

What are two dangers of main electricity?

Fire and electrocution

How are fires caused?

When too high a current is allowed to flow along cables. Current can be limited by placing a fuse or circuit breaker in the live wire.

What is the earth wire used for?

To prevent the metal casing of an appliance from becoming live should a wiring fault occur. A large current flowing down the earth wire will cause the fuse or circuit breaker to isolate the live connection.

Describe how an ammeter should be connected to measure the current through a circuit component and state what its ideal resistance would be

An ammeter measures current. The resistance is 0Ω, as it shouldn’t affect the flow of current.

Describe how a voltmeter should be connected to measure the potential difference across a circuit component and state what its ideal resistance would be

A voltmeter is connected in parallel with the circuit. The ideal resistance of a voltmeter is extremely high, as current shouldn’t affect the circuit.

What happens to the currrent in a series circuit?

It is the same all the way around

What happens to the current in a parallel circuit?

The current splits in a ratio to the resistors

What happens to the voltage in a parallel circuit?

The voltage is the same in parallel

What is one difference between voltage and current?

Voltage doesn’t split, only current splits

What does R_T stand for?

Total resistance

What does EMF stand for?

Voltage of battery or Total Voltage in a series circuit