P1b

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What is infrasound?
Sound waves with a frequency lower than 20 Hz
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State some uses of infrasound
Studying animals, detection of animal movement in remote locations, detection of meteors and volcanic eruptions
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Can humans hear infasound?
No
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Name some animals that communicate using infrasound
Elephants, giraffes and whales
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What is ultrasound?
Sound waves with frequencies higher than 20 000 Hz
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State some uses of ultrasound
foetal scanning, sonar, communication between animals
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Can humans hear ultrasound?
No
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Describe how sonar can be used to find the depth of the sea
a pulse of ultrasound is emitted, then reflected by the sea bed and detected. the time it takes can be used to calculate the distance (d=s x t) the distance must be halved because the ultrasound had to travel to the bottom of the sea and back
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What are seismic waves generated by?
earthquakes and explosions
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Are S waves faster or slower than P waves?
slower
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Are P waves transverse or longitudinal?
longitudinal
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What happens when a seismic wave passes through a different layer of the Earth?
The wave gets reflected and refracted
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Why do seismic waves travel through the earth in a curved line?
Because they are gradually refracted upwards due to a gradual change in density
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How is an earthquake caused?
plates slide past each other, friction builds until there is a sudden jolt
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Why can't scientists predict earthquakes?
They don't know how big the forces acting on the tectonic plates are and they don't know the amount of friction on the plates.
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What is the name of the device used to detect the location of an earthquake?
Seismometer
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How many seismometers are needed to find the location of an earthquake's epicentre?
3
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What is electromagnetic induction?
when a wire is moved inside a magnetic field, creating an induced current
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What is an induced current
current that flows in a wire that is moving relative to a magnetic field
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How do you increase the size of an induced current?
add more turns on the coil, move the coil of wire faster, use a stronger magnet, use an iron core.
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How does a bicycle dynamo work?
the bicycle wheel turns a wire in a magnetic field, creating a current to power the bike's lights.
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How do you change the direction of the induced current?
change the direction of the magnetic field, change the direction of the movement of the wire.
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Does a generator supply an AC or DC current
AC
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Does a bicycle dynamo supply an AC or DC current?
DC
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How does a generator work?
an wire around an iron core spins in a magnetic field, inducing an AC current. The current flows through slip rings then carbon brushes
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What do the slip rings do in a generator?
Make an electrical connection to a circuit. They stop the wires becoming twisted
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What do the carbon brushes do in a generator?
Press against the slip rings to make an electrical connection between the circuit and the spinning coil
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Why is voltage increased before it travels through transmission lines
To decrease current, to minimise heat loss, improving efficiency
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What voltage is the power that flowsinto our homes?
230 V
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Why is voltage decreased before being passed on to our homes, shops and offices?
For safety
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What is a transformer?
Device that changes voltage, it is made up of two coils of wire around an iron core.
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Does a step up transformer increase or decrease voltage?
Increase
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Does a step up transformer increase or decrease current?
decrease
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How is an electric shock caused?
When one part of the body is at a higher voltage than another
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Why do birds not get an electric shock when sitting on an electrical transmission line?
Both their feet are on the wire at the same voltage
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What is power?
Energy transferred per second
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What is power measured in ?
Watts (W)
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What is payback time?
The time it takes to get back in savings the many spent on a change.
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How is payback time calculated?
cost/savings
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Name some ways of reducing energy bills.
Loft insulation, double glazing, hot water tank insulation, draughtproofing, cavity wall insulation, solar panels.
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What is the law of conservation of energy?
Energy cannot be create or destroyed, only transferred to different forms.
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Name the 9 forms of energy.
Nuclear, electrical, sound, chemical, kinetic, heat, light, gravitational potential, elastic potential.
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What is efficiency?
The proportion of energy transferred to useful forms.
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What is the best colour at absorbing thermal energy?
black
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How does a system stay at a constant temperature?
It radiates the same average power as it absorbs.
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Other cards in this set

Card 2

Front

State some uses of infrasound

Back

Studying animals, detection of animal movement in remote locations, detection of meteors and volcanic eruptions

Card 3

Front

Can humans hear infasound?

Back

Preview of the front of card 3

Card 4

Front

Name some animals that communicate using infrasound

Back

Preview of the front of card 4

Card 5

Front

What is ultrasound?

Back

Preview of the front of card 5
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