Energy in appliances Flashcards
.... energy is: Electrical light sound kinetic nuclear thermal gravitational potential elastic potential chemical
whenever a current flows from the sun, light bulbs from loud speakers anything moving has it released only from nuclear reactions flows from hot objects to cooler ones possessed by anything that could fall stretched springs, elastic bands possessed by foods fuels and batteries
What are the three forms of stored energy?
Gravitational, elastic and chemcial
What is the energy principle?
Energy can be transferred usefully from one form to another, stored or dissipated but it can never be stored or destroyed
When only is energy useful? (principle)
When it can be converted from one form to another
What is efficiency a measure of?
How much energy is usefully transferred
What do most appliances or devices do with some of their energy?
Waste it as heat or sound
How do you calculate the efficiency of a machine using it’s energy?
Now it’s power?
Efficiency = useful energy in/ useful energy out Efficiency = useful power in/ useful power out
Why are electrical heater usually 100% efficient?
They spread out all their energy as heat (sometimes some sound though)
Useful energy is …..
All energy eventually ends up as….
Heat is transferred to cooler surroundings which then..
As the heat is transferred it becomes ….. , it …..
The total amount of energy…. ….. …., but the energy has …. out so it can’t be ….. or …. ……
concentrated energy heat warm up concentrated, it dissipates stays the same, spread out, collected, easily reused
What are the advantages and disadvantages with using LED light bulbs ? (2 for each)
They’re: more efficient, last even longer
more expensive, don;t give out as much light
What is the advantage and disadvantage of buying a new more efficient appliance?
What must you do? How?
They’re cheaper to run but expensive to buy
Work out how cost effective it is, by working out the payback time
What do heat exchangers do?
How do they do this? (3 steps)
Reduce the amount of heat energy that is lost
- By pumping cool fluid through the escaping heat
- The temp of the liquid rises as it gains heat energy
- The heat energy in the fluid can then be converted into a useful form, e.g to warm air for the air con in a car
How can you show the efficiency of an appliance in a diagram?
By drawing an energy transformation diagram - a Sankey diagram
Energy =
power x time
What is a kilowatt-hour?
The amount of electrical energy used by a 1kW appliance left on for 1 hour
What does the amount of energy transferred by an appliance depend on?
Its power - how fast it can transfer the energy in the time its on
What is power usually measured in?
What is is the unit for electrical energy?
watts or kilowatts
kilowatt-hours kWh
How do you calculate the cost of electricity? (tow equations)
No. of units of electricity used = power x time
Cost = no. of units x price per unit
How do you find the amount of electricity that has been used on an electricity meter?
Take the original readign from the current reading and that will show how many kWh have been used
If comparing appliances what would you compare? (2)
Cost efficiency
Practicality in areas especially with limited power supplies
What would battery radios be better than clockwork radios where there is no electricity? (2)
What would clockwork radios be better? (3)
You can get new batteries if the power runs out
You don’t have to spend time powering it up
It’s free
You don;t need to live near a town to get new batteries
Better for the environment as batteries contain very harmful chemicals and are tricky to dispose of.
Standard of living is affected by what?
People in MEDCs have ….. ….. but the poorest countries don’t.
Access to electricity
mains electricity
What two useful things are fridges used for?
Why is it devastating not to have them in places?
Keeping food fresh by slowing down the growth of bacteria
They can keep vaccines cold
It’s difficult to distribute vaccinations so will have awful effects on a country’s population
What is electricity good for surrounding public health useful for?
Why is it bad in LEDCs not to have them?
Hospitals in MEDCs heavily rely on electricity e.g x-rays
Without electrical machines diagnosis and treatment of patients would be poorer and could reduce life expectancy
What is it bad not to have electricity for communications in LEDCs?
There are no means of internet, keeping in touch or spreading news and information quickly in an emergency
