Topic 2 - Electricity

Question 1

What is insulation?
What is double insulation?

Answer 1

Insulation is a method of reducing heat transfer (Convection, Conduction, Radiation) between objects.

Double insulation is used in electrical appliances, and uses two layers of insulation to prevent electric shock. This removes the need for an earth wire. The second layer of insulation is often plastic.

Question 2

What is earthing?

Answer 2

Earthing is connecting someone/something to the ground. It has a low-resistance, which allows currents to flow to the ground. As a result, a large amount of current will flow. This will trip the fuse or circuit breaker and stop current flow entirely, preventing electric shocks and damage.

Question 3

What are fuses?
What are circuit breakers?

Answer 3

Fuses are put in electrical circuits and protect against too much current flowing. When too much current flows, they will melt and break the circuit.

Circuit breakers are switches that protect electrical circuits from overloading or short-circuiting. They will detect this and automatically stop the flow of current.

Question 4

What does resistance cause electrical energy to transfer to? What is an example of an appliance aimed at doing this?

Answer 4

Resistance causes electrical energy to transfer to heat/thermal energy. For example, electrical heaters have a high resistance so that a lot of heat is produced.

Question 5

Power = Current x Voltage (P = I x V), but what are the units are rearrangement?

Answer 5

P = I x V
I = P / V
V = P / I

P = Power (Watts, W)
I = Current (Ampere/Amps, A)
V = Voltage (Volts, V)

Question 6

Energy transferred = Current x Voltage x Time (E = I x V x t), but what are the units are rearrangement?

Answer 6

E = I x V x t
I = E / V x t
V = E / I x t
t = E / I x V

E = Energy transferred (Joules, J)
I = Current (Amps, A)
V = Voltage (Volts, V)
t = Time (seconds, s)

Question 7

What is mains electricity? What type of current is it?

Answer 7

Mains electricity is the power on the electrical grid, powering homes, offices, etc. It has a voltage of 230 and a frequency of 50 Hz
It is Alternating Current (a.c.)

Question 8

What current is supplied by a cell or battery?

Answer 8

Direct current (d.c.)

Question 9

Are current, voltage and resistance split, the same or added together in and series and parallel circuit?

Answer 9

Current = Same in Series, Split in Parallel
Voltage = Shared in Series, Same in Parallel
Resistance = Added together in Series and Parallel; however, in Parallel, the reciprocals are added together (image)

Question 10

In what situation would a series or parallel circuit be more useful in a circuit?

Answer 10

A series would be more useful when you want everything to operate as one, and use fewer wires and be cheaper. E.g. Flashlights

A parallel circuit would be useful if you want components to be switched on/off independently, or you want components to still function if one component breaks. E.g. Lighting where you want to operate different lights (have some on, some off).

Question 11

What is the relationship between current and voltage in a:

Fixed resistor

Answer 11

Directly proportional

Question 12

What is the relationship between current and voltage in a:

Filament bulb

Answer 12

Question 13

What is the relationship between current and voltage in a:

Diode

Answer 13

Question 14

What is the relationship between current and voltage in a:

Thermistor

Answer 14

Question 15

What is the relationship between current and voltage in a:

LDR

Answer 15

Question 16

How would you investigate the relationship between current and voltage in different components?

Answer 16

You would use a variable resistor to change the resistance, and then, using a voltmeter and ammeter, measure both to create a table you can draw a graph from.

Question 17

What is the effect on the current of changing resistance?

Answer 17

More resistance = Lower current
Less resistance = Higher current

Question 18

What is the relationship between Light intensity and resistance in an LDR?

Answer 18

More light = Less resistance
Less light = More resistance

Question 19

What is the relationship between temperature and resistance?

Answer 19

More temp = Less resistance
Less temp = More resistance

Question 20

How could you see the presence of current in a circuit using an LED?

Answer 20

The LED will glow more or less depending on the amount of current in the circuit.

Question 21

Voltage = Current x Resistance (V = I x R), but what are the units and rearrangements?

Answer 21

V = I x R
R = V / I
I = V / R

V = Voltage (Volts, V)
R = Resistance (Ohms, Ω)
I = Current (Amps, A)

Question 22

What is the current representation of?

Answer 22

The rate of flow of charge.

Question 23

Charge = Current x time (Q = I x t), but what are the units and rearrangements?

Answer 23

Q = I x t
I = Q / t
t = Q / I

Q = Charge (Coulombs, C)
I = Current (Amps, A)
t = Time (seconds, s)

Question 24

What is electric current in solid metallic conductors?

Answer 24

The flow of negatively charged electrons.

Question 25

What happens to current at a junction, and why?

Answer 25

Current will 'split' at a junction, taking both parts, but at the end it will regroup and remain the same as before Current into a junction = Current out of a junction.

Question 26

What is voltage? What is a volt?

Answer 26

voltage is the energy transferred per unit charge that passes A volt is just a joule per coulomb

Question 27

The equation in E = Q x V, but what are the units and rearrangements?

Answer 27

Energy transferred = Charge x Voltage E = Q x V V = E / Q Q = E / V E = Energy transferred (Joules, J) Q = Charge (Coulomb, C) V = Voltages (Volts, V)

Question 28

What are some common materials that are good electrical conductors, or insulators?

Answer 28

Good conductors (Will conduct electricity) Copper Aluminium Gold Silver Good insulators (will not conduct electricity) Glass Air Plastic Rubber Wood

Question 29

How can you investigate how insulating materials can be charged by friction?

Answer 29

Get a balloon, and rub it against your hair. Electrons will transfer from your hair to the balloon, the balloon will become negatively charged, and the hair will become positively charged. The hair and balloon will then attract towards each other because opposite charges attract.

Question 30

How is a positive or negative charge formed by loss or gain of electrons?

Answer 30

When an atom gains electrons, it has more negatively charged electrons than positively charged protons. This means it will have a negative charge.

Question 31

Like charges ___ Unlike charges ___

Answer 31

Like charges repel Unlike charges attract

Question 32

What causes a balloon to be attracted to your hair?

Answer 32

When you rub the balloon against your hair, electrons move from the hair to the balloon and static electricity builds up, this means the balloon has more electrons than protons (negatively charged) and the jumper has less electrons that protons (positively charged),, as they are unlike charges, they will attract together.

Question 33

What is a potential danger of electrostatic charges?

Answer 33

When refueling an aircraft, fuel moving through a pipe can build up a charge on the pipe due to friction. A buildup of static charge can cause a spark, if the spark is near fuel, it could cause an explosion.

Question 34

What is a use of electrostatic charge? How does it work?

Answer 34

It is used in a photocopier The photoconductor is negatively charged White parts of the paper reflect UV light and release areas of negative charge Toner (ink particles) are positively charged) The toner will be attracted to the areas of negative charge