AQA Physics - P1: Energy

Energy Stores and Systems

• Energy cannot be created or destroyed, only transferred to different energy stores and different objects.
• Energy can be transferred mechanically, electrically, by heating or by radiation.
• Energy in a system (An object or group of objects) can be transferred between objects in the system or between different engery stores.
• In closed systems, the net change of total energy is zero.
• Work done = Energy transferred.
• The eight energy stores you need to know:
• Thermal energy stores
• Kinetic energy stores
• Gravitational potential energy stores
• Elastic potential energy stores
• Chemical energy stores
• Magnetic energy stores
• Electrostatic energy stores
• Nuclear energy stores

Kinetic and Potential Energy Stores

• Kinetic Energy (Ek)
• Anything moving has energy in it’s Ek store. If an object speeds up, energy is transferred to the store and vice versa for slowing down.
• Gravitational Potential Energy (GPE)
• A raised object has energy transferred to the GPE store.
• Falling Objects
• When something falls, the GPE store is transferred to the Ek store. When there is no air resistance, the energy lost from the GPE store is equal to the energy gained in the Ek store.
• Elastic Potential Energy (EPE)
• Stretching or squashing an object transfers energy to it’s EPE store.

Specific Heat Capacity

• Some materials require more energy to be transferred to their thermal stores to increase their temperature. For example, 4200 J is needed to warm 1 kg of water by 1 degree celsius, but only 139 J is needed to warm the same amount of mercury up 1 degree celsius.
• If a material gains loads of energy when heated, they also transfer loads of energy when cooled. They store a lot of energy.
• Specific Heat Capacity is the amount of energy needed to raise the temperature of 1 kg of a substance by 1 degree celsius.