P1.2 - Energy and Efficiency Flashcards
What are the different types of energy?
Electrical energy
Light energy
Sound energy
Kinetic energy
Thermal energy
Gravitational potential energy
Elastic potential energy
Chemical energy
Magnetic energy
What is an example of electrical energy?
Whenever a current flows
What is an example of light energy?
From the Sun, lights, etc
What is an example of sound energy?
Energy released from vibrating objects (noise)
What is an example of kinetic energy?
From movement
What is an example of thermal energy?
Heat energy that flows from hot to cold objects
What is an example of gravitational potential energy?
Possessed by falling objects
What is an example of elastic potential energy?
Stretched springs, elastic, etc
What is an example of nuclear energy?
Released from nuclear reactions
What is an example of magnetic energy?
In magnets, etc
What are gravitational, elastic, and chemical energy examples of?
They are all stored - they are waiting to be turned into other forms of energy.
What is the conservation of energy?
Energy can be transferred usefully from one form to another. It can be stored or dissipated - but it cannot be created or destroyed.
When is energy useful?
Energy is only useful when it can be converted from one form to another.
What are some examples of energy transfer?
Batteries: Chemical energy into Electrical and heat energy
Potential energy (firing a projectile): Elastic into kinetic and heat energy.
Describe what happens in an energy transfer in terms of useful energy.
When useful devices transform energy from one form to another, some of the useful energy is wasted as heat.
When is a device more efficient?
A more efficient device will waste less energy.
What is a machine?
A machine is a device that turns one type of energy into another.
What is the equation for efficiency?
Efficiency = Useful energy or power out/Total energy or power in
Times this by 100 to get it as a percentage.
Why is no device 100% efficient?
The wasted energy is usually spread out as heat.
Why are heaters 100% efficient?
All the energy (wasted or useful) will be useful heat energy.
Describe what happens to wasted energy.
Wasted energy is eventually transferred to the surroundings, which become warmer.
The wasted energy becomes less concentrated and more spread out.
It becomes less useful.
Describe how the choices in light bulbs can differ.
Energy saving bulbs are more cost-effective than ordinary bulbs.
A low-energy bulb is about as 4 times efficient as an ordinary light bulb.
LEDs are more efficient than low energy bulbs and can last longer. However, they are more expensive and do not emit as much light as conventional lights.
How do you work out if an appliance is cost effective?
Work out its payback time.
What do heat exchangers do?
They reduce the quantity of wasted heat energy that is list.
