Download Revision Mat P1_2 - Animated Science

Physics 1 Revision
Energy and Efficiency
Complete the energy transfers below for each
appliance:
TV
Car
Which is the wasted energy from a car, and
what happens to it?
Efficiency is the fraction or percentage of
useful energy an appliance transfers.
Efficiency = _____ energy out / _____ energy In
Efficiency calculation:
What is the efficiency of a hairdryer which uses
1.2kJ of energy and only wastes 120J as sound?
Cost effectiveness and payback time
Payback time (years) = total cost / savings (per years)
For comparing cost effectiveness:
- compare payback times
- look at power used/cost to run (per year/month)
- compare lifetimes of the appliances
Energy and Power
Energy cannot be created or destroyed.
Energy is either transferred usefully or is wasted.
Wasted energy dissipates, heating the surroundings.
The longer something is on, the more energy is uses,
and the more powerful an appliance is, the more
energy is transfers per second.
Energy transferred = Power x time
A kWh is an amount of energy transferred
If the cost per kWh is given, then this is used to
calculate cost of electricity .
Draw a Sankey diagram for a Torch which transfers 800J
Dee
of useful light energy, and 500J of heat energy.
Sankey diagrams:
Useful energy goes across, wasted energy
down. The width of each arrow shows the
amount of energy, and they all add up to the
total input.
Cost calculation
An appliance has a power of 3000W. If 1kWh costs 16
pence, how much does it cost to run the appliance for 150
minutes?
Generating electricity and National Grid
There are many energy sources which can be used to
generate electricity, name 6:
1.
4.
2.
5.
3.
6.
Each way ultimately uses the same method to generate
the electricity. Outline the 3 points in common.
123Dee
Make sure you can give advantages and disadvantages of
each type of power!
Transformers:
Step-up: increase the voltage (potential difference)
Step-down: decrease the voltage (potential difference)
Increasing the voltage ________ the current – this saves
energy loss in cables.