Heat And Energy

Heat is a measurement of energy and is mesured in joules (J) 

The amount of energy needed to raise the temperature of an object depends on:

• The mass of the object
• The change in temperature required
• The material its made from

Total energy supplied=Energy supplied per second X Number of seconds

Eg.= It takes the heater 50 seconds to raise the temperature of the aluminium block by 10'c Calculate the total energy supplied. Remember the heat transfers 100J of heat energy per second.

= 100J/s x 50s = 5000J

Specific Heat Capacity

Each material has a value of how much energy it can hold. This is known as specific heat capacity. Specific heat capacity is the energy needed to raise the temperature of 1kg of material by 1'C.

Energy(J) = Mass (KG) x Specific Heat Capacity (J/kg'C) x Temperature Change('C)

Conductors and insulators

Materials that allows energy to flow through them quickly are called conductors, Metals are good conductors. Materials that allow energy to flow through them much more slowly are called insulators, Most non metals, wood, plastic, glass are good insulators.Curtains are good insulators as they trap a layer of air between them and the window which helps to reduce energy loss.

Saving Energy

• Fibre glass (or mineral wool) for roof insulation(reduces conduction and convection)
• Reflective foil on walls(reduces radiation)
• Foam cavity wall insulation(reduces conduction and convection)
• Double glazing(reduces conduction and convection)
• Draught excluder's(Reduces conduction and convection)

Reducing Heat loss in the home

Payback time (Years) = Cost of installing insulation

                                                    Annual Saving                                                     

Conduction and Convection

Conduction is the transfer of heat energy through a substance from a hotter region to a cooler region without any movement of the substance itself.

Convection is the transfer of heat energy from hotter regions to cooler regions by the movement of particles.

Waves

Transverse Waves have the following features:

• Amplitude
• Wavelength
• Frequency

The electromagnetic spectrum

The electromagnetic spectrum is a continuous spectrum that extends beyond each end of visible spectrum light. It includes microwaves and in fared radiation.

The Wave Equation

Wave Speed (m/s) = Frequency (Hz) x Wavelength (m)

Reflection

Light or another electromagnetic wave can be reflected from multiple surfaces.

Refraction

A wave will speed up or slow down as it passes from one medium (material) into another, This can cause the wave to change direction and is known as refraction.

Diffraction

As waves pass through a gap or an opening (such as a door) the edges spread out This is diffraction. 

What’s in our Universe?

The Universe contains:

• galaxies
• stars
• black holes
• planets
• comets
• meteors.

Galaxies and stars

A star is a huge ball of gas, mostly hydrogen and helium. Nuclear fusion reactions inside the star release enormous amounts of energy. Stars are very hot and give off their own light. This is why we can see the Sun during the day, and distant stars in the night sky.

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M=Mercury 

V=Venus 

E=Earth 

M=Mars 

J=Jupiter 

S=Saturn 

U=Uranus 

N=Neptune 

S=Sedna

Photo Cells, capture light energy from the sun on flat silicon surfaces. The light energy is then transformed into an electric current which travels in the same direction all the time. This is known as an electric current.

Wind Turbines, The suns energy also produces convection currents in the air (wind) Wind turbines transform the kinetic energy of the air into electrical energy. 

The Dynamo Effect,  refers to the way in which electricity can be generated by:

• Moving a wire, or a coil of wire, near a magnet.
• Moving a magnet near a wire or a coil of wire.

When this happens the wire cuts through the lines of force of the magnetic field and a current is produced by electromagnetic induction in the wire (as long as it's part of a complete circuit)

In a generator a coil of wire is rotated in a magnetic field, The coil and the field should be close together.

As the coil cuts through the magnetic field, the relative motion causes a current to be generated in the coil.

The current alternates (it reverses its direction of flow, every half turn of the coil,so a generator produces an alternating current (AC) This is from the direct battery which produces a direct current (DC).

Global Warming

Many greenhouse gases occur naturally, greenhouse gases in the atmosphere trap heat and warm the earth sufficiently to support life. 

Greenhouse gases Include:

• carbon dioxide
• water vapor
• methane

These gases are produced when fuels are burned.

Greenhouse effect

The greenhouse effect occurs because short wavelength electromagnetic radiation from the sun is absorbed by the earth, causing it to heat up. The earth then radiates heats as longer wavelength in fared radiation. Greenhouse gases absorb some of these longer wavelength in fared waves, warming up the atmosphere. 

Alpha, Beta, Gamma

Alpha

The emitted alpha particles ionise air particles and the ions formed are attracted to the oppositely charged electrodes, This produces a current in the circuit.

Beta

A tracer is a small amount of radio active substance that is put into a system so that its progress through the system can be followed using a radiation detector. A beta emitter tracer can be used to observe how elements such as nitrogen and phosphorus move through a plant, from a root to leaf. Beta radiation is used in a paper thickness gauge.

Gamma

Can be used to treat cancer because it destroys cancerous cells. It can also be used to sterilize medical equipment because it can destroy microorganisms like bacteria.