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Flashcards in 4. (a) Electricity Deck (24)
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What is charge measure in



What is electric field

A region in which an electric charge experience a force


What is the line of force

Path a free positive charge would take if released in the field


What is voltage across A and B

Total energy required to move a coulombs of charge from a to b


What is current

The flow of electric charge within a circuit
Measured in A


How to calculate current

Q = I x t


How to calculate resistance

Voltage / current


How to increase resistance

Increase the length of the wire
Reduce the cross section
Increase the temperature


Describe the thermistor

Resistance increase, temperature decrease
Resistance decease, temperature increase


Describe the LDR

Resistance increase, light darker
Resistance decrease, light brighter


Describe the current in series

Current is the same everywhere
I1 = I2 = I3


Describe current in parallel

I total = I1 + I2


Describe the voltage in series

V total = v1 + v2


Describe the voltage in parallel

I Voltage is the same everywhere
V1 = v2 = v3


Describe the resistance in series

R total = r1 + r2


Describe the resistance in parallel

1/ r total = 1/r1 + 1/r2


Explain the term 'digital signals'

A series of pulses consisting of just two states
+ on (1)
+ off (0)
There is no values in between


Explain the term 'analogue signals'

Signals that can vary in frequency, amplitude or both


What are logic gates

Circuits containing transistors and other components
Digital circuit designed to make a decision, it gives an output voltage determined by the input voltage


Describe the danger of damaged insulation in a wire

The layer of insulation around a wire may wear away
A plug or socket may become chipped or broken, exposing a bare wire
Contact with the wire due to gap in insulation causes electric shock


Describe the dangers of overheating cable

Too much current through a wire of a cable -> overheating -> insulation of the wires soften or melt -> exposing wire in the cable
A coiled cable in use could overheat bc the heat has less area to escape -> might cause fire


Describe the dangers of damp conditions in electricity

Water can conduct a current, providing a conducting path to the outer surface
Anyone touching the device could then suffer an electric shock


Describe the use of fuse

Contains a thin wire that heats up and melts if too much current passes through it -> break the circuit
The rating of a fuse is the maximum current that can pass through it without melting the fuse wire


Describe the use of circuit breaker

It is an electromagnetically-operated switch in series with an electromagnet
The switch is held closed by a spring
When the current exceeds a certain value -> the electromagnet pulls the switch open -> current is cut off
They work faster than fuse and can be reset quicker