P1- 2.4

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P1- 2.4- ENERGY AND EFFICIENCY

- Weight is measured in NEWTONS (N)

The weight of a 1 kilogram object of the Earth's surface is about 10N

-Energy is measured in JOULES (J)

The energy needed to lift a weight of a 1N by a height pf 1M is equal to 1J

SANKEY DIAGRAMS:

They are used to show how any energy transfer where energy is wasted

BECAUSE ENERGY CANNOT BE CREATED OR DESTROYED:

INPUT ENERGY= USEFUL ENERGY+ ENERGY WASTED

EFFICIENCY=

USEFUL ENERGY TRANSFERRED BY THE DEVICE

DIVIDED BY

TOTAL ENERGY SUPPLIED TO THE DEVICE

THEN X100 FOR PERCENTAGE

EFFICIENCY LIMITS:

No machine can be more than 100% efficient. We can never get more energy than we put in.

IMPROVING EFFICIENCY:

1. Friction between the moving parts causing heating

Lubricate the moving parts to reduce friction (Applying oil or grease to make them smoother)

2. The resistance of a wire causes the wire to get hot when a current passes through it

In circuits, use wires with as little electrical energy resistance as possible

3. Air resistance causes energy transfer to the surroundings

Streamline the shapes of moving objects to reduce air resistance

4. Sound created by machinery causes energy transfer to the surroundings

Cut out noise (tighten loose parts to reduce vibration)