# Electricity

## Introduction

This topic explores the key concepts of electricity as they relate to:

• static electricity
• current electricity
• higher order models of electric circuits
• household electricity
• electricity and magnetism.

## Key concepts of magnetism

The activities in this topic are designed to explore the following key concepts:

### Static electricity

• Charged objects will attract uncharged objects.
• Objects can be charged by rubbing.
• Some materials are charged more easily than others.
• An object becomes charged when it loses or gains electrons.
• Objects can carry either a positive or negative charge, depending on what they are made of and what they are rubbed with.
• A negatively charged object has gained electrons; a positively charged object has lost electrons.
• Like charges repel; unlike charges attract.
• Charged objects will discharge over time as charge leaks to the atmosphere.
• Charge can move about on conductors, but not very much on insulators.
• Sparks are the movement of electrons through the air from one object to another. Lightning is a sparking effect.
• Earthing is where charge is shared between a charged object and a large conductor (usually the ground).
• We measure the quantity of charge with a unit called a ‘coulomb’.

### Current electricity

• Electric current (measured in amperes) is the flow of electric charge (measured in coulombs) around a circuit.
• A complete circuit is needed for an electric current.
• Conventional current comes out of the positive terminal of a battery and flows back into the negative terminal, whereas electrons actually flow the other way.
• Switches stop the flow of current.
• The current out of the battery from the positive terminal is the same as that entering the battery through the negative terminal. Current is not diminished around a circuit.
• Metals conduct electric current; most other substances are insulators.
• The voltage (measured in volts) of a battery is the energy (measured in joules) supplied to each unit of charge (measured in coulombs).
• Electric circuits involve the transformation of electrical energy into other forms such as heat, light and movement.
• The amount of energy given to each unit of charge diminishes around the circuit.

### Household electricity

• Household electricity runs on 240 volts alternating voltage and current.
• A complete circuit includes the generator, wires and the appliance in the home.
• A fuse or circuit-breaker breaks a circuit when too much current passes through it.
• Households have a number of parallel circuits each with their own fuse or circuit-breaker.
• The wires from the generator are called the active and the neutral. A third wire, the earth, is connected to the neutral wire and the ground.
• The earth wire is not normally part of the circuit. It becomes part of the circuit if it comes in contact with the active wire.
• Physically touching an active wire completes a circuit where the current is passed from the active wire, through the person, the ground and then back to the neutral wire.

## Students' alternative conceptions of electricity

• The electricity companies supply electrons for your household current.
• We pay electricity companies for power.
• 'Static' and 'current' electricity are two types of electrical energy.
• 'Electricity' is used up in electric circuits.
• Charge is used up in electric circuits.
• Energy is used up in electric circuits.
• More devices in a series circuit mean more current because devices 'draw' current.
• Electric power is the same as electric energy.
• Electricity means the same thing as current, or voltage, or energy.
• Batteries store, and supply, electrons or 'electricity' to the electric circuit.
• A wire from a battery to a bulb is all that is needed for the bulb to light up.
• The electric energy in a circuit flows in a circle.
• Electric current is a flow of energy.
• The stuff that flows through wires is called 'electric current'.
• Electrons travel at, or near, the speed of light in the wires of an electric circuit.
• Voltage flows through a circuit.
• Voltage is energy.
• High voltage by itself is dangerous.
• Electrons move by themselves.
• Current is the same as voltage.
• A conductor has no resistance.
• The bigger the battery, the more voltage.
• Batteries create energy out of nothing.
• Alternating current (AC) charges move all the way around a circuit and all the way back.
• AC voltage and current remains constant as in direct current (DC) circuits.

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