Energy and efficiency

Question 1

What is the payback time?

Answer 1

The time it takes to save enough money from heating bills to equal the cost of the initial insulation.

Question 2

what does a U Value show?

Answer 2

It shows how effective a material is as an insulator.

Question 3

What is specific heat capacity?

Answer 3

It tells you how much energy something can store.

Question 4

Whats the formula for specific heat capacity?

Answer 4

E = m × c × θ

The triangle is drawn with the E at the top and the rest under it.

Question 5

What are the units for each part of the E = m × c × θ formula?

Answer 5

E = energy transferred in Joules - J
m = mass in kilograms - kg
c = specific heat capacity - J/kg°C
θ = temperature change -  °C

Question 6

How much energy is needed to heat 2kg of water from 10 - 100°C?

Answer 6

E = m × c × θ

2×4200×90 = 756,000 J

Question 7

What does a low U Value show?

Answer 7

The lower the U-value, the better the material is as an insulator.

Question 8

An empty 200g aluminium kettle cools down from 115 to 10 degrees celsius, losing 19,068 J of heat energy. Whats the specific heat capacity of aluminium?

Answer 8

(Remember the triangle, with E on top)

SHC= 19,068 divided by (105×0.2)

The kettle is 200g so remember to convert into kg!

Question 9

Name the 9 types of energy?

GLETNECKS!

Answer 9

Gravitational Potential,
Light,
Elastic Potential,
Thermal,
Nuclear,
Electrical,
Chemical,
Kinetic,
Sound,

GLETNECKS!

Question 10

What three types of energy are stored energy - Energy not doing anything and waiting to be turned into another form?

Answer 10

The Potentials and Chemical energy:

Gravitational Potential,
Elastic Potential,
Chemical.

Question 11

What is the conservation of energy principle?

Answer 11

Energy can be transferred stored or dissipated but cannot be created or destroyed.

Question 12

When is energy ‘wasted’?

Answer 12

When energy is transferred only part of it may be usefully transferred, the rest is ‘wasted’.

Question 13

What happens to wasted energy?

Why is it less useful?

Answer 13

Wasted energy is eventually transferred to the surroundings, which become warmer.
The wasted energy becomes increasingly spread out and so becomes less useful.

Question 14

What is the formula to calculate efficiency of a device as a percentage?

Answer 14

useful power out efficiency =􏰀 total power in × (􏰁100%)

Question 15

What does ALL energy eventually end up as?

Answer 15

Heat

Question 16

As the heat is transferred to cooler surroundings what happens to the energy?

Answer 16

The energy becomes less concentrated - It dissipates.

Question 17

what are sankey diagrams?

Answer 17

They show how much energy is being usefully used or wasted.

The thicker the arrow the more energy it represents.

Question 18

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

Answer 18

Its power - how fast the appliance can transfer it

The amount of Time its switched on for

Question 19

What is the formula for the amount of energy transferred?

Answer 19

E = P × T

Energy = Power × Time

Question 20

What are the standard units for electrical energy?

Answer 20

Kilowatt-hours kWh
Or
Joules J

Question 21

What are the two different types of units for energy transfer?

Answer 21

E = P × T

Energy = kWh (kilowatt-hours)
Power = kW (kilowatts)
Time = h (hours)

OR

Energy = J (Joules)
Power = W (Watts)
Time = s (secounds)

Question 22

How can you calculate the cost of electricity with two formulas?

Answer 22

E = P × T
C = P × PPU

Cost = E × Price per unit