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Physics Module 4 > Safe Electricals > Flashcards

Flashcards in Safe Electricals Deck (14):
1

Describe and recognise how resistors can be used to change the current in a circuit

A variable resistor (rehostat) has a resistance that can be altered. A current that flows can be changed by simply moving the sliding contact if the variable resistor from one end to another

2

Describe how variable resistors can be used to change the current in a circuit

- longer wires give less current
- thinner wires give less current

3

What is resistance measure in

Ohms

4

Recall the colour coding for live, neutral and earth wires

Live - brown
Neutral - blue
Earth - green/yellow

5

State that an earthed conductor cannot become live

This is because earthing means connecting the conductor to earth, which takes away any charge that could electrocute people

6

Describe reasons for the use of fuses and circuit breakers

They are safety features; prevent fires, injury and death in the home by breaking the circuit of an appliance if a fault occurs

A circuit breaker can be reset. A fuse has to be replaced.

7

Recognise that double insulated appliances don't need earthing

The appliance is a non conductor and cannot become live

8

Explain how variable resistors can be used to change the current in a circuit

Longer wires have more resistance
Thinner wires have more resistance

9

Describe the relationships between current, voltage and resistance:

- for a given resistor, current increases as voltage increases and vice versa
- for a fixed voltage, current decrease as resistance increases and vice versa

10

Equation for resistance

Resistance = voltage / current

11

Describe the functions of the live, neutral and earth wires

Live - carries the high voltage
Neutral - completes the circuit
Earth - a safety wire to stop the appliance becoming live

12

Calculate power

Power = voltage X current

13

Explain how a wire fuse reduces the risk of fire; if the appliance develops a fault:

- too large a current causes the fuse to melt
- preventing flow of current
- prevents flex overheating and causing fire
- prevents further damage to appliance

14

Explain the behaviour of simple circuits in terms of the flow of electric charge

A circuit is a complete loop that allows an electric current to flow. Electrons flow around the circuit from the negative electrode of the power source to the positive electrode.