Enegry stores and systems

Energy is transferred between stores

When energy is transferred to an object, the energy is stored in one of the object's energy stores.The energy stores are:

• Thermal energy stores
• Kinetic energy stores
• Graviatational potential energy stores
• Elastic potential energy stores
• Chemical energy stores
• Electrostatic energy stores
• Nuclear energy stores

Energy is transferred mechanically (by a force doing work), electrically (work done by moving charges) by heating or by radiation. e.g light or sound

When a system changes, Energy is transferred.

• A system is another word for a single object or a group of objects that you're intrested in.
• When a system changes, energy is transferred. it can be transferred into or away from the system, between objects in the system or between different types of energy stores.
• Closed systems where neither matter nor energy can enter or leave. the net change in the total energy of a closed system is always zero.

Energy can be transferred by heating

• Take the example of boiling water in a kettle- you can think of the kettle as the system. Energy is transferred to the water (from the kettle's heating element) by heating, into the water's thermal energy store (causing the temperature to rise).
• You could also think of the kettle's heating element and the water together as a two object system. energy is transferred electrically to the thermal energy store of the kettle's heating element, which transfers energy by heating to the water's thermal energy store.

Energy can be transferred by heating

• Take the example of boiling water in a kettle- you can think of the kettle as the system. Energy is transferred to the water (from the kettle's heating element) by heating, into the water's thermal energy store (causing the temperature to rise).
• You could also think of the kettle's heating element and the water together as a two object system. energy is transferred electrically to the thermal energy store of the kettle's heating element, which transfers energy by heating to the water's thermal energy store.

Energy can be transferred by doing work.Work done is just another way of saying energy transferred- they're the same thing.Work can be done when current flows (work is done against resistance in a circuit or by a force moving an object.The initial force exerted by a person to throw a ball upwards does work. It causes an energy transfer from the chemical energy store if the person's arm to the kinetic store of the ball and arm.A ball dropped dfrom a height is accelerated by gravity. The gravitational force does work. It causes energy to be transferrednfrom the ball's graviational potential energy store to its kinetic energy storeThe friction between a car's brakes and its wheels does work as it slows down. it caused an energy transfer from the wheels' kinetic energy stores to the thermal energy store of the surroundings.In a collision between a car and a stationary object, the normal contact force between the car and the object does work. It causes energy to be transferred from the car's kinetic energy to other energy stores, e.g the elastic potential and thermal energy stores of the object and the car body. Some energy might also be transferred away by sound waves.