Energy sources and Transfer of Energy Flashcards
What is work?
The product of force and distances moved in the direction of the force
Formula and unit for work done
Work done = force x distance moved along the line of action of the force
Unit: Nm or J
A man pressed his hands against a strong wall of height 4m with a force of 30N. Calculate his work done
Work done = force x displacement
30 x 0= 0J
What is energy?
Energy is the ability to do work
What is energy equal to?
Energy = work done
What is the unit of energy?
J or KJ
How many joules is 1KJ?
1 KJ —-> 1000J
Forms of energy (8)
1) Light energy
2) Heat energy
3) Electrical energy
4) Potential energy
5) Sound energy
6) Chemical energy
7) Kinetic energy
8) Wind energy
Sources of energy (6)
1) Solar energy
2) Biomass
3) Geothermal
4) Fossil fuels
5) Batteries
6) Nuclear energy
Types of energy sources (2)
Renewable
Non-renewable
Define renewable energy sources and examples
It is always available. eg. solar, wind, falling water, biomass, geothermal, tidal, wave, hydro-electricity
Define non-renewable energy sources and examples
It will finish eventually. eg. fuel, petrol, kerosene (fossil fuels), nuclear
Advantages of using renewable energy (4)
1) It is always available
2) It is free
3) Available locally
4) Some of them do not cause pollution
What is the principle of conservation of energy?
Energy can neither be created nor destroyed in any process, it can be converted from one form to another.
(Total amount of energy remains constant)
What is kinetic energy?
The energy possessed by any moving object
Formula and unit for kinetic energy
Kinetic energy = 1/2 mass velocity^2
Kinetic energy = 1/2mv^2
Unit: J
What is gravitational potential energy?
The energy possessed by any object due to its height above ground
Formula and unit for gravitational potential energy
G.P.E = mass x gravity x height
G.P.E = mgh
Unit: J
Describe chemical energy
This form of energy is usually stored in food, fossil fuels, batteries and in the re-grouping of atoms during chemical reactions
Describe hydro-electric generation
Water, in lakes on high grounds, stores large amount of gravitational potential energy which is converted to kinetic energy when flowing through pipe to turn the turbines and thus generating electricity
Describe geothermal energy
Large amounts of heat is produced due to nuclear reactions deep in the Earth. Water is channelled through pipes in the hot regions which in turn gets heated until boiling takes place to produce steam. The steam pressure is used to drive the turbines to generate electricity
Describe wind energy
Wind farms are set up in windy regions. The kinetic energy of the wind acts on the long blades of the turbines to generate electricity
Describe solar energy
As a product of nuclear fusion of hydrogen nuclei into helium nucleus, heat energy from the sun reaches the Earth’s surface in the form of electromagnetic waves
How is heat energy from sunlight used? (2)
1) Solar panels absorb the heat from the sunlight to heat water which is then stored in an insulated tank
2) Photovoltaic cells are installed on the roof of houses and commercial buildings to produce their own electricity
Describe nuclear fission
Common in a nuclear reactor of nuclear power station. This reaction can be controlled. A large nucleus is split into two or more light nuclei of comparable sizes and large amounts of heat energy is released
Describe nuclear fusion
It occurs in the sun. Two light nuclei of hydrogen fuse together to produce a heavy nucleus of helium and huge amount of heat energy produced. A very high temperature is needed for nuclear fusion to occur.
During a nuclear reaction where is the large amount of heat energy derived from?
A mass defect
What is power?
The rate at which work is done
Formulas and units for power
Power = work done ÷ time
OR
Power = energy ÷ time
Units: J/s or W
Formula for % efficiency
% efficiency = output power ÷ input power x 100
Formula for efficiency
Efficiency = output power ÷ input power
What are possible reasons for power waste? (2)
1) Loss of energy due to friction
2) Work done against air resistance
What are some common energy conversions? (4)
1) Filament lamp
2) Hair dryer
3) Fluorescent lamp
4) Coal-fired power station
Advantages (2) and disadvantages (2) of solar energy
Advantages: No pollution. Renewable
Disadvantages: Expensive. Limited use in certain areas without continuous sun
Advantages (1) and disadvantages (4) of nuclear energy
Advantages: Large amount of energy is released
Disadvantages: Expensive to set up. Uses high technology. High level of precautions. Danger from radioactive radiations that may cause cancer
Advantages (2) and disadvantages (3) of biofuel
Advantages: Renewable. Easy to produce
Disadvantages: Causes pollution in the atmosphere. Disruption of scenery. Large plot of land is required for disposal of wastes for decomposition
