Unit 1 Chapter 2 - Using Energy

Question 1

Conservation of Energy

What is the rule of conservation of energy?

What happens to waste energy?

Answer 1

ENERGY CANNOT BE DESTROYED OR CREATED.

The total energy before = the total energy after

This is the CONSERVATION OF ENERGY

Energy that is not useful in certain situations dissipate into the surroundings. One example would be heat when a tyres of a car produce friction.

Question 2

Useful energy

What is wasted and useful energy?

What happens to energy?

Answer 2

Useful energy is transferred where it is WANTED.

Wasted energy is energy that is NOT usefully transferred.

WHAT HAPPENS TO ENERGY?

• Wasted energy dissipates to the surroundings.
• Useful energy eventually transfers to its surroundings too.
• Energy becomes less useful the more it spreads out for e.g.

Energy supplied to heat buildings will eventually be transferred to the surroundings.

Question 3

Energy and efficiency

How do sankey diagrams work?

Efficiency equation?

Answer 3

Energy is measured in joules (J). The energy needed to lift an object of 1 newton by a height of 1 metre is equal to 1 joule.

Useful and wasted energy can be represented by SANKEY DIAGRAMS.

Input energy = wasted + useful energy

Efficiency = useful energy transferred to device/ total energy supplied to device.

Question 4

Forms of energy

What are the different forms of energy?

What is the process of energy transfer in a microwave?

What is the process of energy transfer when a block is dropped from a height?

Answer 4

Energy can be in various different forms:

• Chemical Energy
• Kinetic energy
• Gravitational potential energy
• Elastic potential energy
• Electrical energy
• Thermal energy
• Light energy
• Sound energy

Energy transfers from one form to another e.g. Microwave oven:

Chemical energy (battery) > electrical energy > light energy + energy heating surroundings

E.g. 2

When a block falls:

Gravitational P.E > energy > Heat (friction) + sound (on impact)