power

Question 1

deifne POWER

Answer 1

rate of doing work measured in watts

and is a scalar quantitiy

Question 2

what is formula for power in terms of work done

Answer 2

power = work done / time taken

Question 3

what does the total amount of energy transfer depend on

ie. 2 factors

Answer 3

power rating and length of tiem of use

Question 4

what is the formula for power output of a moving object that is subject to a force

and significance of each symbol

Answer 4

p = F x V

f is force

v is velocity

Question 5

what is the equation for efficiency in terms of energy and power

x2 eqs

Answer 5

useful output energy / total input energy x 100%

useful output power/ total input power x100%

Question 6

what is the energy input of each.
What is the energy output of each.

electric motor

solar cell

rechargeable battery

electric radiatior

power station

car (petrol)

car (diesel)

steam engine

Answer 6

1. electrical to kinetic/potential
2. light to electrical
3. electrical to electrical
4. electrical to thermal
5. nuclear to electrical
6. chemical to kinetic/potential
7. chemical to kinetic/potential
8. chemical to kinetic/potential

Question 7

how do power stations transfer electrical energy in our homes

Answer 7

fuels are used to transfer heat energy

the heat energy heats water so that high pressured steam can be blown onto turbines, which turn generators

then use national grid to transfer electrical energy

Question 8

how to draw a sankey diagram for power production problem.

eg. you burn 3000MW of fuel, you get 1000MW of electrical energy and 5 different waste energy.

Answer 8

make a rectangle with 3000MW

make 1 arrow from that rectangle of 1000MW horizontally shows the useful energy output

then make other arrows below that line for wasted energy outputs