Energy Flashcards
What was the concept of energy originally used for?
Emerged in the 19th century and used to explain the work output of steam engines and then generalised to understand other heat energies. Became a key tool for understanding chemical reactions.
What are critical energy problems for this century?
The use of fossil fuels and global warming.
What is a system?
An object/ group of objects
What happens when a system changes?
When a system changes, energy is transferred either into or away from the system, between different objects in the system or between different energy stores.
What are the 8 energy stores?
Thermal energy Kinetic energy Gravitational potential energy Elastic potential energy Chemical energy Magnetic energy Electrostatic energy Nuclear energy
When an object is projected upwards how is energy changed?
Energy shifts from chemical energy stores if the body to the GPE store if the objects via the work done by forces.
When a moving object hits an obstacle how is energy changed?
Energy shifts from kinetic energy store of object to the thermal and elastic potential energy stores via work done by forces.
When an object accelerates by a constant force how is energy changed?
Energy shifts from chemical store of fuel to the kinetic store of the object.
When a vehicle slows down how is energy changed?
Energy shifts from kinetic store of the vehicle to thermal store of the breaks via friction between a car’s brakes and its wheels.
When a water is brought to the boil in an electric kettle how is energy changed?
Energy shifts from chemical store of the fuel (at the power station) to the thermal store of the water.
What is internal energy?
The total kinetic and potential energies of all the particles that make up a system.
What does doing work on a system increase?
The energy stored in a system.
What does heating a system do?
It increases the energy of the particles within it.
What happens as energy in a system increase?
It either increases the temperature or produces a change of state.
What does an increase of temperature in a system depend on?
- The mass of the substance heated
- What the substance is
- The energy input
What is specific heat capacity?
The specific heat capacity if a substance is the amount of energy required to raise the temperature of 1kg of the substance by 1 degree Celsius.
What is power?
The rate at which energy is transferred or at the rate at which work is done.
What is the power of 1 watt equal to?
1 joule per second.
What is a closed system?
A system where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero, but the energy can be transferred from one store to another.
Energy can not be created or destroyed but…
Transferred usefully, dissipated or stored.
What happens when a lift raises in the lift carriage?
It transfers electrical energy to GPE
Some energy is dissipated into the surroundings as heat and sound
This wasted energy is no longer available for useful transfers
What is wasted energy caused by?
By unwanted energy transfers
How can unwanted energy transfers be reduced?
- lubrication reduces friction that causes heat.
- tightening any loose parts- prevents unwanted vibrations that waste energy as sound
- Thermal installation reduces heat walls.
How do cavity walls (thermal insulation) reduces heat loss?
They are made up of inner and outer wall with an air gap in the middle- the air gap reduced the amount of energy lost by conduction. Cavity wall installation is where the gap is filled by foam can reduce energy transfer by convection.
