1. Topic 4

2. Hearing Range
The frequency range audible to humans is from 20Hz to 20,000Hz. Below 20Hz are infrasounds, above 20,000 Hz are ultrasounds.

3.
Sonar uses pulses of ultrasound to find the depth of water beneath a ship
The ship emits a pulse of ultrasound sound down into the sea.
This spreads out through the water and some is reflected by the sea bed.
The sound echoes back from the seabed and travels back up to the ship.
Microphone detectors on the ship detect the echo.
Sonar equipment measure the time between the sound being sent out and echo returning.
The depth of the water can be calculated using the equation.
Distance = speed x time

4. Ultrasound is used to scan for foetus
Ultrasound waves are used to make images of things inside the body.
Ultrasound are not harmful so it is safe to use them to scan detailed images of unborn babies.
A gel is used to stop the ultrasound reflecting from the skin.
The probe emits and receives ultrasound waves.
Some sound is reflected when the ultrasound waves pass into a different medium, suck as fat or bone.
The ultrasound machine detects the time between sending the pulse out and receiving echo. The display shows where the echoes came from.
The further down the screen, the longer the echo took to get back to the machine.

5. Seismometer Seismic Waves (P and S Waves)
In an earthquake there are 2 types of waves given off P and S waves
P Waves
these area the first to reach a detector
They are longitudinal waves
They can travel through liquid and solid parts of the earth.
S Waves
These arrive second.
They are transverse waves.
They can only travel through the solid part of the earth so are stopped by the liquid core
All seismic waves can be detected using an instrument called
Seismometer

6. Higher tier only
Part of the wave is reflected at the boundaries between different layers
Seismic waves from an earthquake travel through the Earth.
The speed of the seismic waves changes with depth because the rocks have different properties. The gradual change in wave speed makes the waves travel along a curved path

7. Explain how seismic waves can be used to find out where an earthquake happened.
Seismic waves spread out in all directions from the point where the earthquake happens.
Seismic waves are detected using a seismometer.
P waves travels faster than S waves so they are detected first.
The greater the distance between the earthquake and the seismometer, the greater the difference in time of arrival of the P waves and S waves.
Distance from at least three seismometers in different places are used to work out where the earthquake happened.

8. Finding the epicentre
The difference in the time taken for the S-waves and the P-waves to arrive can tell us how far away the earthquake is. If 3 stations are used then the exact location of the epicentre can be found by drawing a ring of the correct distance around each station. Where the 3 rings cross is where the earthquake started.

10. Speed m/s metres per second Time s seconds
Answers:
Distance m metres
Speed m/s metres per second
Time s seconds
Wave speed m/s metres per second
Frequency Hz hertz
Wavelength m metres
Energy J joules
Power W watts
Current A amps
Voltage V voltage
What is the unit for?
Distance
Speed
Time
Wave speed
Frequency
Wavelength
Energy
Power
Current
Voltage

11. TOPIC 5

12. Renewable Resources Solar Tidal Hydroelectric Wind Geothermal Wave
How they work:
Advantages
Disadvantages
Solar
Solar cells heat air under glass, hot air rises and turns gen
Direct transfer of energy (non-lost)
Have to be in a specific area, only works with light
Tidal
Tides move through a dam turning a turbine
Direct energy transfer
Predictable
Have to have a tide
Not available all year round
Hydroelectric
Falling water in high reservoirs
Available at any time Started and stopped easily
Reservoirs can dry up
Need rainfall to refill them
Wind
Turns a wind turbine directly generating electricity
Need a lot to produce electricity
Dependant on wind
Geothermal
Heat is transferred by hot underground rocks
No harmful gasses
No fuel cost
Need to be by a tectonic plate (location)
Wave
Floating electrical generators. Air forced up pipes, turns a gen
Not predictable
Don’t work in bad weather

13. Non-Renewable Resources
Advantages
Disadvantages
Coal
Formed from fossilised plants
Ready-made fuel.
It is relatively cheap to mine and to convert into energy.
When burned they give off atmospheric pollutants, including greenhouse gases
Oil
A carbon-based liquid formed from fossilised animals.
Gas

14. Generating Electricity
Electromagnetic induction – creates a current in a wire when a wire is moved into a magnetic field The current can be increased by: • Using a coil of wire, or putting more turns on the coil • Using an iron core inside the coil of wire • Using stronger magnets • Moving the wire faster The direction of the current can be changed by changing the direction: • Of the movement of the wire • Of the magnetic field Direct current (DC) - current flows in one direction Alternating current (AC) – current changes direction Generators supply current with alternates in direction (AC)

15. Transformers in the local sub-stations reduce the voltage to 230 V.
The voltage is increased by the transformer to VOLTS to prevent energy being WASTED as HEAT in the transmission lines.
This improves efficiency.

16. Transmitting Electricity
A transformer can change the size of an alternating current If the voltage passed through the nation grid is increased less energy is wasted as heat and the efficiency is improved Power stations convert 25kV to 400kV before the electricity is sent around the country • A step up transformer – increases the voltage and decreases the current. This happens between power station and transmission lines to stop heat being wasted. • A step down transformer – decreases the voltage and increases the current. This happens between local substations and homes to reduce the voltage for homes

19. Topic 6

20. In other words, 1 Watt = 1 Joule per second
Energy and Power
The POWER RATING of an appliance is simply how much energy it uses every second.
In other words, 1 Watt = 1 Joule per second E T P
Converting units
Kilojoules to joules x1000
Kilowatts to watts x1000
Minutes to seconds x60
Hours to minutes x60 then x60 again to get to seconds.
E = Energy (in joules)
P = Power (in watts)
T = Time (in seconds)
Using the formula triangle, write an equation to calculate:
Energy
Power
Time

21. Payback time= Cost / savings per year
Reducing Energy Use
Payback time= Cost / savings per year
Years Pounds (£)
Cost Efficient means which is the best value for money
Payback time how long it will take to make the money back in relation to savings

22. Calculating the Cost of Electricity
To work out how much a device costs we do the following:
Cost of electricity = Power (kW) x time (h) x cost per kWh (p)
For example, if electricity costs 8p per unit calculate the cost of the following…
A 2kW fire left on for 3 hours
A 0.2kW TV left on for 5 hours
A 0.1kW light bulb left on for 10 hours
A 0.5kW hoover left on for 1 hour
48p 8p 8p 4p

25. Sankey Diagrams:
These show energy conservation, the width of the arrows represents the amount of energy in joules.

26. Efficiency
How good a device is at converting energy into useful forms is know as its efficiency. Low energy light bulbs transfer more of the input electrical energy, into light electricity than older light bulbs which produce excess heat.

27. Efficiency Calculation

28. Earth’s energy balance
The Earth’s surface absorbs about half of the radiation that reaches it from the Sun. It re-radiates this energy as IR, which can warm up the atmosphere. For the temperature of the Earth to stay the same, it must radiate energy into space at the same average rate it is absorbed.

29. How changes in the atmosphere can warm the Earth…
Explain what the greenhouse effect is and what causes it…