30 terms

# IGCSE Physics: Electricity

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Double insulated
As well as their wiring being insulated, the outer casing of the appliance is also made of an insulating material, usually plastic.
Fuses
These are fitted in plugs and are heatproof tubes containing a wire designed to melt when a specified current is exceeded, therefore cutting off live supply.
Circuit breakers
They perform the same job as fuses, breaking the live connection when a specified current is exceeded.
Power
The rate at which electrical energy is converted in an appliance. Measured in watts.
Current
The rate of flow of electric charge through a conductor. Measured in amps.
Voltage
The amount of energy is transferred per coulomb of charge that is passed through the battery. Measured in volts.
Alternating current
Causes the current to change continuously, with electricity flowing in one direction then the other.
Direct current
Causes electricity to flow in one direction only.
Conductors
Materials that conduct electricity well. They are usually metallic.
Insulators
Materials that do not conduct electricity at all. They are usually non-metallic; rubber, glass and many types of plastic.
Atom
Made up of neutrons and protons which make the nucleus, which is surrounded by fast moving electrons.
Proton
Positively charged particles in the nucleus of an atom.
Neutron
Neutral particles in the nucleus of an atom.
Electrons
Negatively charged particles which surround the nucleus of an atom.
Positive
A material has this charge when it loses electrons.
Negative
A material has this charge when it gains electrons.
Free electrons
Electrons that are not bound to any particular atom in the structure of the metal, they are free to move at random throughout the metal.
Electric charge
Measured in coulombs.
Ammeter
A device used to measure current.
Series ciruit
A circuit in which all parts are connected end to end to provide a single path of current.
Parallel circuit
A closed electrical circuit in which the current is divided into two or more paths and then returns via a common path to complete the circuit.
Resistance
The opposition posed by a material or a device to the flow of current. Measured in ohms.
Voltmeter
A device used to measure voltage, or electrical potential energy difference.
Fixed resistor
Resistors that have a value that cannot be changed.
Variable resistor
A resistor whose value can be varied between its minimum and maximum values.
Thermistor
A resistor that changes its resistance with a change of temperature.
LDR
A device whose resistance depends on the amount of light. An increase in light causes a decrease in resistance.
Switch
A device for making, breaking, or changing the connections in an electrical circuit.
LED
A diode that will produce light when current flows through it.
Diode
A device that permits current to flow through it in only one direction.