Physics !

Infrared Radiation is energy transfer by electromagnetic waves.

All objects emit infrared radiation.

The hotter an object is the more radiation it emits in a given time.

Dark, matt surface emit infrared radiation more quickly than light, shiny surfaces.

They also absorb infrared radiation more quickly than light,shiny surfaces.

Light, shiny surfaces reflect more infrared radiation than dark, matt surfaces.

Particles in a solid are in a close, fixed positions, vibrating.

Particles in a liquid are still toucing but are able to move alot more in a random way. 

Particles in gas move freely and are not touching eack other. 

Metals are best conductors.

Good insulators are materials like wool and fibreglass.

Conduction occurs best in metals due to the free electrons transferring energy.

Non-metals are poor conductors due to the lack of free electrons. 

Convection is the circulation of a fluid caused by heat.

ONLY in liquids and gases. 

Heating cause the fluid to be less dense so rises and causes circulation.

Evaporation and condensation

• Evaporation = liquid to gas
• Condensation = gas to liquid 

Energy Transfer by design

•   The rate of energy transfer to or from an object depends on:
  • the shape, size and type of material of the object
  • the materials the object is in contact with
  • the temperature difference between the object and it's surroundings

The greater the mass of an object, the more slowly it's temperature increases when heating

The rate the temperature change in a substance when heating depends on the energy transfer to it, its mass and its specific heat capacity.

Heating and insulating buildings

 We can reduce our energy transfer to and from our homes.

U-values tells us how much energy passes per second through materials.

The lower the U-Value, the better the material.  

Energy can be found in may forms.

We can transfer one form of energy to another form

Different types : Light, Sound, Kinetic, nuclear, electrical, gravitational potential, elastic potential and chemical.

Conservation of energy. 

Energy can be transferred from one form to another or from one place to another place.

Energy is not created or destroyed.

Energy that is in place and is in the form we need is known as useful energy. 

Energy that is not useful is known as wasted energy.

 Both sorts of energy both end up in the surroundings as heat energy. 

As the energy spreads out, it is more difficult to use for further energy transfers. 

Useful energy transferred by the appliance        

Total energy supplied to the appliance            (x100%)

• Measures to make machines more efficient include reducing:
  • friction
  • air resistance
  • electrical resistance
  • noise due to vibrations 

Energy can be turned to useful energy with the flick of a switch on appliances

Electrical appliances are designed for specific purposes and are designed to lose as little energy as possible

Electrical Power

Power is the rate of energy transfer.

Efficiency=useful power energy out      (x100%)

                   total power in 

The kilowatt hour is the energy supplied to a 1kW appliance in 1 hour

E= P x t   

E= energy transferred in kWh

P= power of the appliance (kW)

t= time taken (hours) for energy to transfer.

Total cost + number of kWh x cost per kWh

Means getting the best value of money.

To compare the cost effectiveness of different appliances, we need to take account of a number of different costs. 

These may include:

•  
  • the cost of the appliance
  • cost of insulation
  • running costs
  • Maintenance costs 
  • environment costs
  • interests on loans  

The generators in power stations are driven by turbines

Coal, oil and natural gas are burnt to turn the turbines.

Uranium and plutonium is used as the fuel in nuclear power plants.

Biofuels are renewable sources of energy used to generate energy.

Wind turbines are electrical generators on top of a tall tower and is driven by a wind turbine.

Waves generate electricity by turning a floating generator.

Hydroelectricity generate electricity by running water down hill turning turbines.

A tidal power station traps high tides and uses it to turn turbines

Solar cells transfer solar energy directly into electricity.    

Solar heating panels use the suns energy to heat water directly

Geothermal energy come from the Earth.

Burning fossil fuel creates greenhouse gases that cause global warming.

Nuclear fuel produce radioactive waste. 

Using renewable resources can affect animal and plant life

The National Grid

The national grid distributes electricity from power stations to our home

Step-up and step-down transformers are used in the national grid. 

A high grid voltage reduces energy wastage and makes it more efficient.

Waves are used to transfer energy and information

Transverse wave = vibrate at a right angle to the direction of energy

Longitudinal waves = vibrate parallel to the direction of the energy

Mechanical waves need a medium (substance) to travel through. These waves can be transverse or longitudinal waves. i.e air.

Measuring Waves (P1 5.2)

Amplitude= height of the wave crest

Frequency= number of wave crests

Wavelength= distance from one wave to another wave

V = f x 

The normal of a point in the line drawn perpendicular to the surface.

Angles are always measured between the light ray and the normal.

The angle of incidence and the angle of reflection are always equal stated in the laws of reflection

Refraction (P1 5.4)

Refraction in light is the change in direction of a light ray when it crosses a boundary between two transparent substances.

If the speed is reduced, refraction is towards the normal.

If the speed is increased, refraction is away from the normal.

This is the spreading out of waves. This occurs when they pass through a gap or round the edge of an obstacle.

The narrower the gap = the increase in diffraction. 

If radio waves didn't diffract enough when going over obstacles i.e hills. then we would receive poor radio/TV signal. 

Sound (P1 5.6)

The normal human ear can hear the frequency range of 20Hz - 20kHz

These waves are longitudinal waves 

They need a medium

Echoes are the reflection of sound

Pitch increase the frequency. i.e if the pitch of a note was high, the frequency would be high.

Loudness depends on the amplitude of the wave.

Sound from instruments is due to vibrations.

Radio, Microwaves, Infrared, Light, Ultraviolet, X-rays, Gamma Rays

V = f x       can be used to calculate the frequency and wavelength of the electromagnetic waves. 

Radio, microwaves, infrared, light (P1 6.2)

White light contains all the colours of the spectrum.

These are all ways of communication

Radio waves of different frequencies are used for various purposes

Microwaves = satellite tv signal

Optical fibres are used to transmit signals by light and infrared radiation. 

The expanding universe (P1 6.4)

Light from different galaxies is red shift.

Red-shift is evidence that the universe is expanding. 

The universe started with a Big Bang. This was a huge explosion from a very tiny part.

From that part of history, the universe has not stopped, it is continuously expanding.

Cosmic microwave background radiation (CMBR) is electromagnetic waves created just after the Big Bang.

At this moment in time, CMBR can only be explained by the Big Bang theory.