4. (a) Electricity Flashcards

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0
Q

What is electric field

A

A region in which an electric charge experience a force

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1
Q

What is charge measure in

A

Coulomb

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2
Q

What is the line of force

A

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

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3
Q

What is voltage across A and B

A

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

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4
Q

What is current

A

The flow of electric charge within a circuit

Measured in A

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5
Q

How to calculate current

A

Q = I x t

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6
Q

How to calculate resistance

A

Voltage / current

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7
Q

How to increase resistance

A

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

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8
Q

Describe the thermistor

A

Resistance increase, temperature decrease

Resistance decease, temperature increase

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9
Q

Describe the LDR

A

Resistance increase, light darker

Resistance decrease, light brighter

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10
Q

Describe the current in series

A

Current is the same everywhere

I1 = I2 = I3

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11
Q

Describe current in parallel

A

I total = I1 + I2

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12
Q

Describe the voltage in series

A

V total = v1 + v2

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13
Q

Describe the voltage in parallel

A

I Voltage is the same everywhere

V1 = v2 = v3

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14
Q

Describe the resistance in series

A

R total = r1 + r2

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15
Q

Describe the resistance in parallel

A

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

16
Q

Explain the term ‘digital signals’

A

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

17
Q

Explain the term ‘analogue signals’

A

Signals that can vary in frequency, amplitude or both

18
Q

What are logic gates

A

Circuits containing transistors and other components

Digital circuit designed to make a decision, it gives an output voltage determined by the input voltage

19
Q

Describe the danger of damaged insulation in a wire

A

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

20
Q

Describe the dangers of overheating cable

A

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

21
Q

Describe the dangers of damp conditions in electricity

A

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

22
Q

Describe the use of fuse

A

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

23
Q

Describe the use of circuit breaker

A

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