P1.2 Energy and Efficiency

Question 1

Energy cannot be _____ or _____.

However, it can be _____, _____ or _____.

Answer 1

CANNOT: created or destroyed
CAN: transferred usefully, stored, or dissipated

Question 2

What happens to wasted energy? (2)

Answer 2

• DISSIPATES/is transferred to surroundings and warms them

- Becomes increasingly SPREADS OUT, so less useful

Question 3

What equation is used to calculate efficiency?

Answer 3

Useful energy (or power) out/Total energy (or power) in
x100

Question 4

What does ‘pay-back time’ measure?

Answer 4

How cost-effective an energy-saving solution is

Question 5

Give 2 advantages of replacing an old appliance with a new, more efficient one

Answer 5

• Costs less TO RUN

- Uses/wastes less energy

Question 6

Give 2 disadvantages of replacing an old appliance with a new, more efficient one

Answer 6

• Cost/difficulty of disposal

- Old one goes to landfill

Question 7

What is the equation for pay-back time?

Answer 7

Cost of installation/Savings per year in fuel costs

Question 8

What are the four ways that a machine can waste energy?

Answer 8

• FRICTION between moving parts= heating
• RESISTANCE of the wire=heating when a current passes through
• AIR resistance
• SOUND

Question 9

How can friction be prevented in a machine?

How do you prevent the resistance of a wire in a machine?

Answer 9

Lubricate the moving parts

Use wires with a resistance as low as possible

Question 10

How do you prevent air resistance of a moving object?

How do you lessen noise from a machine?

Answer 10

• Streamline the shape of the moving object

- Tighten loose parts to reduce vibrations