Energy in appliances

Question 1

.... energy is:
Electrical
light
sound
kinetic
nuclear
thermal
gravitational potential
elastic potential
chemical

Answer 1

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

Question 2

What are the three forms of stored energy?

Answer 2

Gravitational, elastic and chemcial

Question 3

What is the energy principle?

Answer 3

Energy can be transferred usefully from one form to another, stored or dissipated but it can never be stored or destroyed

Question 4

When only is energy useful? (principle)

Answer 4

When it can be converted from one form to another

Question 5

What is efficiency a measure of?

Answer 5

How much energy is usefully transferred

Question 6

What do most appliances or devices do with some of their energy?

Answer 6

Waste it as heat or sound

Question 7

How do you calculate the efficiency of a machine using it’s energy?
Now it’s power?

Answer 7

Efficiency = useful energy in/ useful energy out
Efficiency = useful power in/ useful power out

Question 8

Why are electrical heater usually 100% efficient?

Answer 8

They spread out all their energy as heat (sometimes some sound though)

Question 9

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 …. ……

Answer 9

concentrated energy
heat
warm up
concentrated, it dissipates 
stays the same, spread out, collected, easily reused

Question 10

What are the advantages and disadvantages with using LED light bulbs ? (2 for each)

Answer 10

They’re: more efficient, last even longer

more expensive, don;t give out as much light

Question 11

What is the advantage and disadvantage of buying a new more efficient appliance?
What must you do? How?

Answer 11

They’re cheaper to run but expensive to buy

Work out how cost effective it is, by working out the payback time

Question 12

What do heat exchangers do?

How do they do this? (3 steps)

Answer 12

Reduce the amount of heat energy that is lost

1. By pumping cool fluid through the escaping heat
2. The temp of the liquid rises as it gains heat energy
3. 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

Question 13

How can you show the efficiency of an appliance in a diagram?

Answer 13

By drawing an energy transformation diagram - a Sankey diagram

Question 14

Energy =

Answer 14

power x time

Question 15

What is a kilowatt-hour?

Answer 15

The amount of electrical energy used by a 1kW appliance left on for 1 hour

Question 16

What does the amount of energy transferred by an appliance depend on?

Answer 16

Its power - how fast it can transfer the energy in the time its on

Question 17

What is power usually measured in?

What is is the unit for electrical energy?

Answer 17

watts or kilowatts

kilowatt-hours kWh

Question 18

How do you calculate the cost of electricity? (tow equations)

Answer 18

No. of units of electricity used = power x time

Cost = no. of units x price per unit

Question 19

How do you find the amount of electricity that has been used on an electricity meter?

Answer 19

Take the original readign from the current reading and that will show how many kWh have been used

Question 20

If comparing appliances what would you compare? (2)

Answer 20

Cost efficiency

Practicality in areas especially with limited power supplies

Question 21

What would battery radios be better than clockwork radios where there is no electricity? (2)
What would clockwork radios be better? (3)

Answer 21

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.

Question 22

Standard of living is affected by what?

People in MEDCs have ….. ….. but the poorest countries don’t.

Answer 22

Access to electricity

mains electricity

Question 23

What two useful things are fridges used for?

Why is it devastating not to have them in places?

Answer 23

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

Question 24

What is electricity good for surrounding public health useful for?
Why is it bad in LEDCs not to have them?

Answer 24

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

Question 25

What is it bad not to have electricity for communications in LEDCs?

Answer 25

There are no means of internet, keeping in touch or spreading news and information quickly in an emergency