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Types of Energy Mechanical energy: Potential + Kinetic = Work 1. Work is done when a force acts on an object to cause it to move, change shape, displace, or do something physical. 2. Mechanical energy is energy in an object due to its motion, or position, or both 3. In order for work to be done, an object has to supply a force for another object to be displaced (moved from it’s place Most potential energy Changing from potential to kinetic energy 6. The hammer used both potential & kinetic energy to drive the nail. Mechanical energy results in work being done Thermal (heat) Energy Energy from the internal motion of atoms 1. Thermal energy is energy that comes from temperature of matter. A swimming pool at 40°C is at a lower temperature than a cup of tea at 90°C. However, the swimming pool contains a lot more water. Therefore, the pool has more thermal energy than the cup of tea even though the tea is hotter than the water in the pool. Let us see this example below: If we want to boil the water in these two beakers, we must increase their temperatures to 100°C. You will notice that will take longer to boil the water in the large beaker than the water in the small beaker. This is because the large beaker contains more water and needs more heat energy to reach 100°C. 3 types of energy transfer: • Conduction • Convection • radiation Conduction: the direct transfer of heat from one substance to another substance that it is touching 3. Conduction: when a substance is heated, its particles gain energy and vibrate more vigorously. The particles bump into nearby particles and make them vibrate more. For conduction to occur, the objects must be touching Convection: the transfer of heat by the movement of a liquid or gas 4. Convection: when particles in liquids and gasses get warm, they become less dense (more loose) and they rise. The space is quickly replaced by cooler particles that are more dense. Radiation: The transfer of heat by electromagnetic waves 5. Radiation: all objects transfer thermal energy by infra-red radiation. The hotter an object is the more infra-red radiation it gives off. Chemical Energy: Energy that is released from chemical reactions – when the bonds of atoms are broken 1. Chemical energy is stored energy in the bonds of chemical compounds (atoms & molecules). It is released in a chemical reaction. 3. The chemical energy stored in food is measured in kilocalories or calories. 4. How is the stored chemical energy of coal released to produce electricity? By burning or boiling. Electrical Energy: Energy from the movement of electrons. 1. Matter is made up of atoms. In these atoms, there are even smaller stuff called electrons that are constantly moving. 2. We generate electrical energy when we cause the electrons to move from one atom to another with the use of magnetic forces. If you look at a battery, it will have two ends: a positive terminal and a negative terminal. If you connect the two terminals with wire, a circuit is formed. Electrons will flow through the wire and a current of electricity is produced. 3. What is one example of electrical energy that doesn’t need a wire? Energy can be stored in many ways. Then it can be transferred into other kinds of energy Energy transfer: a. The sun transfers thermal (heat) energy to plants, humans & animals b. Rivers, streams and waterfalls are sources of water (hydro) energy c. When humans eat plants, their stored energy is transferred to us and we use the energy to do work d. The sun transfers heat energy to bodies of water. The warm water heats the air above it. The warm air rises, so the air now is moving so it has kinetic energy e. Moving air (kinetic energy) turns blades to generate wind energy – which is used to generate electrical energy f. Energy from the sun (solar energy) is captured and then transferred to electrical energy Energy Dissipation 1. As the pool ball is hit, the kinetic energy decreases as it moves along. 2. Kinetic energy has been dissipated through friction