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:
- 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’.
- 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 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
Research into students' ideas about this topic has identified the following non-scientific conceptions:
- 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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