Energy - Forces doing Work Flashcards
(25 cards)
What happens to energy when systems change?
Energy is stored in different ways or transferred between stores.
How can energy transfers be represented?
Using diagrams like flow charts or Sankey diagrams.
What is the total energy change in a closed system?
There is no net change in total energy; it is conserved.
Name three ways energy can be changed in a system.
By forces doing work, in electrical equipment, or through heating.
How is work done measured?
By measuring the force applied and the distance moved in the direction of the force.
What is the formula for work done?
Work done = force × distance moved in the direction of the force (E = F × d)
What is the unit for work done?
The joule (J).
What is meant by doing work on an object?
Transferring energy to the object by applying a force.
What type of energy does work done against friction often become?
Thermal energy (heat).
How can you calculate energy changes from work done?
By using the formula E = F × d.
What happens to energy during inefficient mechanical processes?
It is dissipated to the surroundings, often as heat.
What causes energy dissipation in mechanical processes?
A rise in temperature due to friction or resistance.
What is power?
The rate at which energy is transferred or work is done.
What is the formula for power?
Power = energy transferred ÷ time (P = E/t)
What is the unit of power?
The watt (W).
How many joules per second is one watt?
One watt is equal to one joule per second (1 W = 1 J/s).
How is efficiency calculated?
Efficiency = useful energy transferred / total energy supplied
What is energy efficiency expressed as?
A decimal or percentage.
How can efficiency be improved?
By reducing energy losses, e.g., through insulation or lubrication.
Give an example of energy transferred by work done by forces.
Lifting an object increases its gravitational potential energy.
Give an example of energy transfer in electrical equipment.
A kettle transfers electrical energy to thermal energy in water.
Give an example of energy transfer through heating.
A radiator transfers thermal energy to a room.
What is wasted energy?
Energy not usefully transferred, often lost as heat or sound.
Why is reducing energy dissipation important?
To improve efficiency and reduce energy use.
