• Energy is the ability to make things happen or, as scientists say, do work.
• Energy comes in many forms, from the chemical energy locked in sugar to the mechanical energy in a speeding train.
• Energy does its work either by transfer or conversion.
• Energy transfer is the movement of energy from one place to another, such as heat rising above a fire or a ball being thrown.
• Energy conversion is when energy changes from one form to another — as when wind turbines generate electric power, for instance.
• Energy is never lost nor gained; it simply moves or changes. The total amount of energy in the Universe has stayed the same since the beginning of time.
• Power stations do not create energy. They simply convert it into a convenient form for us to use electricity.
• Wind farms can be constructed in areas where there is a steady wind. About 47% of the kinetic energy of the wind can be harnessed.
• Energy and mass are actually the same thing. They are like opposite sides of a coin and are interchangeable.
• Potential energy is energy stored up ready for action — as in a squeezed spring or stretched piece of elastic.
• Kinetic energy is energy that something has because it is moving, such as a rolling ball or a falling stone.
• Kinetic energy increases in proportion with the velocity of an object squared. So a car has four times more kinetic energy at 40 km/h than at 20 km/h.
• Energy is measured in joules (J). One joule is the energy involved in moving a force of one newton over one meter
• A kilojoule (kJ) is 1000 joules.
• A calorie was the old measure of energy, but is now used only for food: 1 calorie is 4187 J; 1 Cal is 1000 calories.
• For scientists, ‘work’ is the transfer of energy. When you move an object, you do work. The work done is the amount of energy (in joules) gained by the object. A A hydroelectric power station is a device that converts the energy of moving water into electrical energy. 152
• For scientists, `power’ is the work rate, or the rate at which energy is changed from one form to another.
• The power of a machine is the amount of work i does divided by the length of time it takes to do it.
• The power of a car’s engine is the force with which the engine turns multiplied by the speed al which it turns.
• A transducer is a device for turning an electrical signal into a nonelectrical signal (such as sound) or vice versa. A loudspeaker is a transducer.
• The energy in the Big Bang was 1068 J. The world’s coal reserves are 2 x 1023 J; thunderstorm has 1 14 J of energy; a large egg has 400,000 J.
• When sleeping you use 60 Cats an hour and 80 Cals when sitting. Running uses 600 Cals. Three hours of reading or watching TV uses 240 Cals. Seven hours’ hard work uses about 1000 Gals — or about 10 eggs’ worth.