Electricity

Question 1

What does insulation, earthing, fuses and breakers do?

Answer 1

Protects the device or user in domestic appliances from being electrocuted

Question 2

What does current in a resistor result in?

Answer 2

The transfer of energy and an increase in temperature. This can be useful for a kettle or microwave

Question 3

What is the formula for power?

Answer 3

Current * voltage

Question 4

What is the formula for energy transferred?

Answer 4

current * voltage * time

Question 5

What is mains supply (a.c.)?

Answer 5

The current is constantly changing direction

Question 6

What is battery supply (d.c.)?

Answer 6

The current will always flow in the same direction

Question 7

What does current in a series circuit depend on?

Answer 7

The applied voltage and the number of other components in that series circuit.

Question 8

How does a light dependent resistor change resistance?

Answer 8

In bright light the resistance falls and in darkness the resistance increases

Question 9

How does a thermistor change resistance?

Answer 9

In hot conditions the resistance drops and in cool conditions the resistance goes up

Question 10

What can indicate presence of current in a circuit?

Answer 10

Lamps and LEDs

Question 11

What is the formula for voltage?

Answer 11

current * resistance

Question 12

What is the definition for current?

Answer 12

The rate the charge flows

Question 13

What is the formula for charge?

Answer 13

Current * time

Question 14

In parallel circuits how do you find the current?

Answer 14

You add all the components currents together

Question 15

In parallel circuits how do you find voltage?

Answer 15

Voltage is the same across all branches

Question 16

What is the definition for voltage?

Answer 16

Energy transferred per unit charge passed

Question 17

What is the definition for a volt?

Answer 17

Joule per coulomb

Question 18

What is the formula for energy transferred?

Answer 18

Charge * voltage

Question 19

Why is fuelling aircraft and tankers dangerous?

Answer 19

1) As the vehicle is fuelled static is built up
2) This can lead to a spark which will result in an explosion

Question 20

How do inkjet printers work?

Answer 20

1) Drops of ink are forced out of a nozzle making them electrically charged
2) The droplets are deflected as they pass between the two metal plates
3) The droplets are attracted to the plate of the opposite charge and repelled from the plate with the same charge
4) The size and direction of the voltage across each plate changes so each droplet is deflected to hit a different place on the paper

Question 21

How do photocopiers work?

Answer 21

1) The image plate is positively charged. An image of what your copying is projected
2) Whit bits of what your copying make light fall on the plate and the charge leaks away in those places
3) The charged bits attract negatively charged black powder which is transferred onto positively charged paper
4) The paper is heated so the powder sticks