Sound And Mains Electricity Flashcards
How are sound waves produced?
They’re produced by vibrations travelling through the air
What type of waves are sound waves?
Longitudinal because air particles vibrate along the direction in which the waves transfer energy
Can sound waves travel through a vacuum?
No, sound needs a medium to travel
What’s the pitch of a note and what’s it measured in?
The pitch is how fast something is vibrating. The number of vibrations per second is called the frequency it’s measured in Hertz(Hz)
What are two ways you can make a guitar string vibrate more quickly?
Lighter, thinner string
Tighter string
What’s the loudness of a sound ?
The loudness depends on amplitude(size of the vibrations from the rest position)the bigger the vibration the louder the sound
How do different frequencies of sound appear on an oscilloscope?
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
How do different amplitudes of sound appear on an oscilloscope?
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
What’s the audible range for humans?
20Hz-20,000Hz
What’s an experiment for measuring the speed of sound?
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
What is the equation linking speed, distance and time?
Speed(m/s) = distance(m)/time(s)
Why does sound travel faster in solids and liquids than gases?
Sound wave vibrations travel faster in a solid because the particles are closer together so the particles knock into each other quicker.
What is the wiring like in households?
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
What’s the live wire and what does it do?
- the live wire is brown
- provides electricity to the appliance
What’s the neutral wire and what does it do?
- neutral wire is blue
- completes the circuit and brings electricity back
What’s the earth wire and what does it do?
- 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
Why is the outer casing of a plug made of plastic?
For insulation so you don’t get an electric shock
Why are plug pins made of brass?
- it’s a good conductor
- durable, sturdy and not malleable
What’s the purpose of the cable grip in a plug?
To secure the cable in place so the wires don’t move from their place and cause a safety risk
What’s the circuit symbol?
Two rectangles on top of each other
What’s the purpose of a fuse in a plug?
- 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
What does a circuit breaker do?
If too large a current flows in a circuit, a switch automatically opens making the circuit incomplete.
What are two advantages of circuit breakers over fuses?
- you don’t have to replace anything with a circuit breaker
- circuit breaker is faster at breaking a circuit than a fuse
How does the earth wire act as a safety measure?
- 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
What’s double insulation?
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
What’s the heating affect of current?
Heating appliances have wires with high resistance so electrical energy is converted into heat energy
What’s the equation linking power, current and voltage?
Power(W) = current(A) x voltage(V)
What’s the equation linking energy transferred, power and time?
Energy transferred(J) = power(W) x time(s)
What’s direct current?
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
What’s alternating current?
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
What’s the equation for frequency ?
Frequency = 1/t
What’s a division?
Each square on a graph
What are the three wires in a plug connected to?
Earth pin
Live pin
Neutral pin
