Sound And Mains Electricity

Question 1

How are sound waves produced?

Answer 1

They’re produced by vibrations travelling through the air

Question 2

What type of waves are sound waves?

Answer 2

Longitudinal because air particles vibrate along the direction in which the waves transfer energy

Question 3

Can sound waves travel through a vacuum?

Answer 3

No, sound needs a medium to travel

Question 4

What’s the pitch of a note and what’s it measured in?

Answer 4

The pitch is how fast something is vibrating. The number of vibrations per second is called the frequency it’s measured in Hertz(Hz)

Question 5

What are two ways you can make a guitar string vibrate more quickly?

Answer 5

Lighter, thinner string

Tighter string

Question 6

What’s the loudness of a sound ?

Answer 6

The loudness depends on amplitude(size of the vibrations from the rest position)the bigger the vibration the louder the sound

Question 7

How do different frequencies of sound appear on an oscilloscope?

Answer 7

The higher the frequency the more squashed up a wave appears in one second the lower the frequency the more stretched out the wave appears in one second

Question 8

How do different amplitudes of sound appear on an oscilloscope?

Answer 8

The bigger the amplitude the taller the wave appears, amplitude is a measure of how much a wave has been displaced from its rest position

Question 9

What’s the audible range for humans?

Answer 9

20Hz-20,000Hz

Question 10

What’s an experiment for measuring the speed of sound?

Answer 10

1) measure 50m from a large flat outdoor wall
2) create a sound(such as a clap) and check you can hear an echo from the wall not from any other walls in the area
3) now clap repeatedly so you can only hear your clap not the echo
4) measure the time it takes to clap 10 times and repeat this 5 times to then get an average
5) you then use the equation speed =distance/time

Question 11

What is the equation linking speed, distance and time?

Answer 11

Speed(m/s) = distance(m)/time(s)

Question 12

Why does sound travel faster in solids and liquids than gases?

Answer 12

Sound wave vibrations travel faster in a solid because the particles are closer together so the particles knock into each other quicker.

Question 13

What is the wiring like in households?

Answer 13

Electrical energy enters through cables which then connected to an electricity meter which is then directed to a fuse box which contains fuses or circuit breakers, from the fuse box wires are connected to ring main circuits than are hidden in the walls and floors of each room, electrical appliances are connected into these ring mains using plugs

Question 14

What’s the live wire and what does it do?

Answer 14

• the live wire is brown

- provides electricity to the appliance

Question 15

What’s the neutral wire and what does it do?

Answer 15

• neutral wire is blue

- completes the circuit and brings electricity back

Question 16

What’s the earth wire and what does it do?

Answer 16

• earth wire is green and yellow
• it’s there as a safety measure, if the live wire frays onto a metal casing of an appliance the earth wire provides a low resistance path for the electricity to flow down

Question 17

Why is the outer casing of a plug made of plastic?

Answer 17

For insulation so you don’t get an electric shock

Question 18

Why are plug pins made of brass?

Answer 18

• it’s a good conductor

- durable, sturdy and not malleable

Question 19

What’s the purpose of the cable grip in a plug?

Answer 19

To secure the cable in place so the wires don’t move from their place and cause a safety risk

Question 20

What’s the circuit symbol?

Answer 20

Two rectangles on top of each other

Question 21

What’s the purpose of a fuse in a plug?

Answer 21

• the fuse contains a thin piece of metal that has a low melting point
• if there’s too large of a current the fuse melts(blows)
• the circuit is then incomplete this prevents you from getting an electric shock and reduces the possibility of an electrical fire
• once the fault has been corrected the blown fuse must be replaced for the appliance to be used again

Question 22

What does a circuit breaker do?

Answer 22

If too large a current flows in a circuit, a switch automatically opens making the circuit incomplete.

Question 23

What are two advantages of circuit breakers over fuses?

Answer 23

• you don’t have to replace anything with a circuit breaker

- circuit breaker is faster at breaking a circuit than a fuse

Question 24

How does the earth wire act as a safety measure?

Answer 24

• if an appliance has a metal casing this should be connected to the earth wire
• so if the live wire becomes damaged or breaks and comes into contact with the casing the earth wire provides a low resistance path for the current
• this current will blow the fuse so the circuit will be broken

Question 25

What’s double insulation?

Answer 25

When there’s a plastic casing over all of the outside of an appliance so that if the live wire came loose you wouldn’t get an electric shock and there’s no need for an earth wire

Question 26

What’s the heating affect of current?

Answer 26

Heating appliances have wires with high resistance so electrical energy is converted into heat energy

Question 27

What’s the equation linking power, current and voltage?

Answer 27

Power(W) = current(A) x voltage(V)

Question 28

What’s the equation linking energy transferred, power and time?

Answer 28

Energy transferred(J) = power(W) x time(s)

Question 29

What’s direct current?

Answer 29

Batteries and cells provide a current that is always in the same direction which is shown on an oscilloscope as a straight line with a consistent current value
Current flowing in one direction

Question 30

What’s alternating current?

Answer 30

Like the mains supply it’s when voltage value increases and decreases. This happens because of the way electricity is produced in power staitions
Current that flows in one direction then the other

Question 31

What’s the equation for frequency ?

Answer 31

Frequency = 1/t

Question 32

What’s a division?

Answer 32

Each square on a graph

Question 33

What are the three wires in a plug connected to?

Answer 33

Earth pin
Live pin
Neutral pin