GCSE OCR GATEWAY PHYSICS ENERGY COMPLETE REVISION SUMMARY

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This page contains the detailed and easy notes for GCSE OCR Physics Energy for revision and understanding Energy.

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GCSE OCR ENERGY Complete Revision Summary

ENERGY

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ENERGY

DIFFERENT FORMS OF ENERGY

Kinetic energy: kinetic energy is the energy stored in something that moves.
Light energy: energy carried by the wavelength of a photon.
Gravitational energy: the energy of gravity or the work done against gravity.
Thermal energy: thermal energy is the heat or vibration of atoms.
Electricity: the energy carried by the movement of electrons.
Chemical energy: chemical energy is the energy contained in the bonds between atoms in molecules.
Nuclear energy: energy stored in the nuclei of atoms. The nucleus of each atom is composed of neutrons and protons that are held together by strong bonds of energy.
Sound energy: the energy of the vibrations that travel through a fluid.
Magnetic energy: correlated to electrical energy, magnetic energy is also a product of the movement of electrons and their ability to produce a field.

FORMS OF ENERGY

ENERGY	DEFINATIONS	EXAMPLE
Thermal Energy	Energy from the heated objects.	Energy in Kettle
Light Energy	Energy that helps to see.	Bulb, Torch
Electrical Energy	Energy due to the flow of charge or current	Electrical Appliances
Chemical Energy	Energy stored in the chemical bonds	Food, Batteries
Sound Energy	Energy due to vibrations	Loudspeaker
Nuclear Energy	Energy stored in the nucleus of the atom	Nuclear Reactor
Kinetic Energy	Energy due to movement	Roller coaster moving down
Potential Energy	Energy due do the position	Ball raised to a height
Elastic Energy	Energy stored in stretch objects	Springs, Rubber

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ENERGY TRANSFER

Law of Conservation of Energy: Energy is neither created nor destroyed. It changes from one form to another.

At the extremes pendulum gains kinetic energy.
As it comes back to mean position kinetic energy converts to gravitational potential energy.
It goes to a height and gains potential energy.

The potential energy is converted into kinetic energy when it moves.

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Energy (1)

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WORK AND ENERGY FORMULAE

Potential Energy P.E = m x g x h

Potential energy in Joules (J) g is the gravitational field strength in N/kg, and h is the height in metres (m).

Kinetic Energy K.E = ½ mv²

m is the mass in kilograms(kg), v is the speed(m/s) and the kinetic energy in joules(J).

Elastic Potential Energy E.P.E. = ½ ke²

Elastic potential energy in joules (J), k is the spring constant in N/m and e is extension in metres (m).

Efficiency = useful output/ Total input x 100

Efficiency is the relationship between the useful work done by a machine, an engine, a device, etc. And the energy supplied to it, often expressed as a percentage.

m: mass of the object
g: Acceleration due to gravity
v: velocity of an object
k: spring constant
e: extension

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Examples

Q1 Calculate the work done when 2 N of force moves a block to a distance of 2 m

W =F x S = 2 x 2 = 4J

Q2 Calculate the kinetic energy when a 2kg block moves at the speed of 3 m/s

K.E = ½ mv²

½ x 2 x 3² = 9J

Q3 Calculate the potential energy when the mass of 2 Kg is raised to a height of 5m above the ground.

P.E = mgh

2 x 10 x 5 = 100J (g = 10m/s²)

Q4 Calculate the energy dissipated by a 10 W bulb in 2 minutes

E = P x t

= 10 x 2 x 60

= 1200J

HOOKE’s LAW

The extension produced in an elastic object is directly proportional to the force applied on it.

F ∝ e

F = ke

Elastic Potential Energy = ½ ke²

ENERGY EFFICIENCY

Energy efficiency, means using less energy to provide the same level of energy.

All appliances do not convert 100% of the input energy into useful energy.

The waste energy is dissipated to the surroundings.

Energy efficiency = Useful/total x 100

= 90/100 x 100

= 90%

USEFUL AND WASTE ENERGY

Device	Useful Energy	Waste Energy
	Light Energy	Heat Energy
	Kinetic Energy	Heat and Sound Energy
	Heat Energy	Light and Sound

FRICTION

Friction is the force that opposes the motion of the body.

It results in loss of energy.

Methods to prevent friction:-

a) Lubricate, paint or smooth the surface by regular oiling of the machines
b) Streamline the body of the object like ship or plane to cut down air resistance
c) Tighten the loose parts to prevent friction and reduce sound energy.

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HEAT TRANSFER

CONDUCTION

The process by which heat is transferred by the direct contact of the particles and the particles vibrate and conduct heat.
Greater the transmission greater is the thermal conductivity of the material.

CONVECTION

Heat transfer through fluids in which the hot molecules rises and the cold molecules sink generating a convection current.

RADIATION

The process of heat transfer by electromagnetic radiation. There is not a direct contact between the two surfaces.
The stove element heats the kettle and the kettle heats the water by conduction. Water circulating in the kettle transfers heat by convection. Near the stove, air would feel warm due to heat transfer by radiation.

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GREENHOUSE EFFECT

It is the natural process that warms the surface of the Earth.
When the Sun’s energy reaches the Earth’s atmosphere, part of it is reflected in space and the rest is absorbed and re-irradiated by greenhouse gases.
Greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs).
The energy absorbed warms the atmosphere and the surface of the Earth. This process keeps the Earth’s temperature at about 33 degrees Celsius warmer than it would be, allowing life on Earth to exist.

ENERGY LOSS IN HOMES

LOFT INSULATION

Uses fibre glass in the loft.
Fibre glass is an insulator and prevents the heat loss by conduction.
Thicker the layer better the conduction.

CAVITY WALL INSULATION

It is the insulation between the two layers of the bricks.
The insulation between the bricks traps air and prevent loss of energy by conduction.

DOUBLE GLAZING

Thicker glass with dry air or vaccum in between.
Glass has lower conductivity and air act as an insulator prevent loss by conduction.
The vaccum prevent loss by convection.

THICK BRICKS

Thick bricks with lower thermal conductivity prevents the loss of heat by conduction.

FOILING

Foiling between the radiator and the panel reflect the heat back into the home and prevent it from escaping.

SOURCES OF ENERGY

RENEWABLE

The source of energy that can be replinished and will never run out.
Eg – Solar, Wind, Geothermal
Does not produce any harmful or greenhouse gases

NON RENEWABLE

The source of energy that cannot be replinished and will run out.
Example: Fossil Fuels like coal, petrol, natural gas
Produces harmful greenhouse gases.

BIOFUELS

Making methane, ethanol or other fuel by using plant and animal waste which is :
Biofuels convert the energy of the sun into plant materials, which are then processed to produce liquid fuels.
Biofuels include ethanol, which can be replaced by gasoline in many recent model cars.
For this reason, biofuels are particularly useful for meeting the energy needs of the transport sector.

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RENEWABLE SOURCE OF ENERGY

ENERGY ISSUES

Reliability

Cost

Demand – With the increase in global energy demand, common fossil fuels that produce energy, such as coal, oil and natural gas, are running out

Supply

KEY TERMS

Kinetic energy: kinetic energy is the energy stored in something that moves.
Gravitational Potential energy: the energy of gravity or the work done against gravity.
Elastic Energy – Elastic energy is the potential energy stored as a result of the deformation of an elastic object, such as the stretching of a spring.
Work Done – Work is done when a force moves something over a distance.
Power – power is the rate of doing work or of transferring heat,
Energy efficiency – means using less energy to provide the same level of energy.
Useful Energy – Energy transferred in the form and where it is desired
Waste Energy – The energy which is transferred to the surroundings is wasted.
Friction – Friction is the force that opposes the motion of the body.
Conduction – The process by which heat is transferred by the direct contact of the particles and the particles vibrate and conduct heat.
Convection – Heat transfer through fluids in which the hot molecules rises and the cold molecules sink generating a convection current.
Radiation – The process of heat transfer by electromagnetic radiation. There is not a direct contact between the two surfaces.
Greenhouse Effect – It is the natural process that warms the surface of the Earth.
Renewable Energy – The source of energy that can be replinished and will never run out.
Non renewable Energy – The source of energy that cannot be replinished and will run out.
Biofuel – Biofuels convert the energy of the sun into plant materials, which are then processed to produce liquid fuels.
Tidal Energy – It is a form of hydropower that converts the energy obtained from tides into useful forms of power, mainly electricity.
Solar Energy – Radiation from the Sun capable of producing heat, generating electricity.

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Disclaimer:

I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.

References:

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Question by Topic

Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.

Energy

Energy Transfer By Heating

Energy Resources