Topic 10 Electricity - Definitions (Higher) - PMT Extended

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Alternating Current
Current flow consisting of charges that continually change direction. These oscillations usually occur at a set frequency.
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Ammeter
A device connected in series with a component to measure the current that flows through it.
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Amperes
The unit of current.
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Circuit Breaker
A safety device that cuts off the power supply if a surge of current passes through it. Circuit breakers can be reset and are quicker acting that fuses.
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Coulomb
The unit of charge.
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Currents at a Junction
The sum of the currents entering a junction must always equal the sum of the currents leaving it. This is a consequence of the conversation of charge.
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Diode
A component that only allows current to flow through in the forward direction. They have very large resistances in the reverse direction.
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Direct Current
Current flow consisting of charges flowing in a single direction only. Batteries and cells provide direct current.
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Earth Wife
The green and yellow striped safety wire connected to metal casings, that prevents an appliance from becoming live.
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Electric Current
The rate of flow of electrical charge. Its value is the same at any position in a single close loop. In metals, the charges that flow are electrons.
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Energy Transfers in Circuits
Electrical energy is transferred to thermal energy when current does work against a resistance. In metals this is a result of collisions between electrons and ions.
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Filament Lamp
A light emitting component consisting of an enclosed metal filament. Its resistance increases as the filament's temperature increases.
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Light Dependent Resistor (LDR)
A light sensitive component whose resistance decrease as its temperature increases.
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Light Emitting Diode
A device that gives out light when a current flows through it. Current can only flow through it in one direction, and a minimum voltage must be applied across it before it illuminates.
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Live Wire
The brown coloured wire that carries the alternating current from the supply in a mains power supply.
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Mains Electricity
An a.c supply, which in the UK has a frequency of 50Hz and a value of 230V.
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Neutral Wire
The blue coloured wire that completes the circuit in a mains power supply.
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Ohmic Conductor
A conductor whose current flow is directly proportional to the potential difference across it, when held at a constant temperature.
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Ohms
The unit of resistance.
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Ohm's Law
The current flowing through an Ohmic conductor at constant temperature is directly proportional to the potential difference across it.
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Parallel
Components connected in parallel have the same potential difference across each component. The total current is equal to the sum of the currents flowing through each component.
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Potential Difference
The energy that is transferred per unit charge between two points in a circuit. It is often also called a voltage.
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Power
The rate at which an appliance transfers energy. For a circuit component, it is equal to the product of the current passing through it and the potential difference across it.
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Resistance
A measure of the opposition to current flow.
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Resistors in Parallel
The total resistance is less than the lowest individual resistance.
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Resistors in Series
The total resistance is equal to the sum of the resistances of the individual resistors.
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Series
Components connected in series have the same current passing through each component but share the total potential difference of the power supply.
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Thermistor
A temperature dependent component, whose resistance increases as is temperature decreases.
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Volt
The unit of potential difference. One volt is equal to one joule per coulomb.
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Voltmeter
A device that is connected in parallel with a component to measure the potential difference across it.
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Watt
The unit of power.
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Other cards in this set

Card 2

Front

Ammeter

Back

A device connected in series with a component to measure the current that flows through it.

Card 3

Front

Amperes

Back

Preview of the front of card 3

Card 4

Front

Circuit Breaker

Back

Preview of the front of card 4

Card 5

Front

Coulomb

Back

Preview of the front of card 5
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