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Physics 1 - Motion, Forces And Conservation Of Energy > Efficiency > Flashcards

Flashcards in Efficiency Deck (16):
1

what is the aim of energy efficiency

the aim of energy efficiency is to use less energy to provide the same service

2

how can energy efficiency be increased in the homes of people using electrical appliances

reducing standby times of electrical appliances

3

formula for calculating kinetic energy

KE = (1/2mass) x v^2

4

what is wasted energy

wasted energy is the percentage of energy that isnt transferred to the energy stores of the device or is used to fulfil its function

5

what is the wasted energy from a lightbulb and how is it wasted

- the wasted energy is thermal energy it gives off
- this energy is dispersed to the thermal energy stores of the surroundings

6

how can heat loss be reduced in a house other than with cavity walls and why does this work

- double glazing windows
- because air is trapped between the windows so the heat has to be transferred through it
- but air is a lower thermal conductivity than solids
- so the heat from the house is lost at a slower rate

7

what general method can be used to reduce energy loss

- cogeneration
- this consists of putting wasted energy (byproduct) of a machine to use by using it to power something else
- like transferring the heat given off by a generator to the thermal energy stores of water to heat it

8

when is energy only useful

when it is transferred from one store to another useful store

9

what can useful devices do

transfer energy from one store to a useful store

10

how is some of the input energy from a store to a useful store usually lost as

it is lost or dissipated to the thermal energy stores of the surroundings

11

how is efficiency decreased when work is done mechanically

- frictional forces have to be overcome
- like moving parts rubbing or air resistance
- the energy needed to overcome these frictional forces
- is transferred to the thermal energy stores of whatever is doing the work
- and the surroundings

12

explain the energy transfers of a motor lifting a load

- energy is transferred electrically to the motor by the mains supply
- the motor transfers useful energy from its kinetic energy stores to the kinetic and gravitational potential energy stores of ghe load
- but it also transfers energy mechanically to the thermal energy stores of the moving parts
- and electrically to the thermal energy stores of the circuit
- the energy is dissipated, heating the surroundings

13

what is the conservation of energy principle

total energy output = useful energy output + wasted energy

14

what does the conservation of energy principle mean

the less energy that is wasted, the more efficient the device is said to be

15

what is the formula for efficiency

- efficiency = useful energy transferred by device (J) / total energy supplied to device (J)
- multiply the calcluation by 100 to get the percentages

16

is a fluorescent bulb more efficient than a filament bulb and if so, why

- the fluorescent light bulb is more efficient than an incandescent flashbulb
- as it uses less electrical energy