4. (a) Electricity

Question 0

What is electric field

Answer 0

A region in which an electric charge experience a force

Question 1

What is charge measure in

Answer 1

Coulomb

Question 2

What is the line of force

Answer 2

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

Question 3

What is voltage across A and B

Answer 3

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

Question 4

What is current

Answer 4

The flow of electric charge within a circuit

Measured in A

Question 5

How to calculate current

Answer 5

Q = I x t

Question 6

How to calculate resistance

Answer 6

Voltage / current

Question 7

How to increase resistance

Answer 7

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

Question 8

Describe the thermistor

Answer 8

Resistance increase, temperature decrease

Resistance decease, temperature increase

Question 9

Describe the LDR

Answer 9

Resistance increase, light darker

Resistance decrease, light brighter

Question 10

Describe the current in series

Answer 10

Current is the same everywhere

I1 = I2 = I3

Question 11

Describe current in parallel

Answer 11

I total = I1 + I2

Question 12

Describe the voltage in series

Answer 12

V total = v1 + v2

Question 13

Describe the voltage in parallel

Answer 13

I Voltage is the same everywhere

V1 = v2 = v3

Question 14

Describe the resistance in series

Answer 14

R total = r1 + r2

Question 15

Describe the resistance in parallel

Answer 15

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

Question 16

Explain the term ‘digital signals’

Answer 16

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

Question 17

Explain the term ‘analogue signals’

Answer 17

Signals that can vary in frequency, amplitude or both

Question 18

What are logic gates

Answer 18

Circuits containing transistors and other components

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

Question 19

Describe the danger of damaged insulation in a wire

Answer 19

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

Question 20

Describe the dangers of overheating cable

Answer 20

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

Question 21

Describe the dangers of damp conditions in electricity

Answer 21

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

Question 22

Describe the use of fuse

Answer 22

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

Question 23

Describe the use of circuit breaker

Answer 23

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