Energy Transfers + Effeciency

Question 1

Heating

Answer 1

Energy is transferred from one object to another object with a lower temperature

Question 2

Waves

Answer 2

Waves eg light and sound can transfer energy

Question 3

Electricity

Answer 3

An electrical current can transfer energy

Question 4

Forces/Mechanical work

Answer 4

Energy is transferred when a force moves or changes the shape of an object

Question 5

Examples

Answer 5

Person throwing a ball up - energy in chemical energy store of person is transfer mechanically - force applied on the ball to kinetic energy store of the ball

Car accelerating- energy in chemical energy store from petrol reacts with the engine and transfers energy mechanically to the Kinect energy stores of the car.

Question 6

Examples

Answer 6

Car braking - friction between the car brakes and wheels cause work to be done which cause energy in the kinetic energy store to be transferred mechanically to the thermal energy store of the surroundings - road and air.

Car crash - kinetic energy store transferred mechanically to the thermal energy store of the wall as there’s a force acting on it from the car.

Question 7

Open system and closed

Answer 7

Open - exchange energy and matter with their surroundings.

Closed - they don’t let matter in or out but can exchange nergy

Question 9

How to improve efficiency

Answer 9

Reducing wasted energy transfers. They waste energy mainly due to -
Friction between their moving parts, air resistance, electrical resistance, sound.

Most of these lead to thermal energy being dissipated into the surroundings. If u can minimize these then improve the efficiency of a device

Question 10

Efficiency

Answer 10

A ratio of the amount of useful energy that’s given out to the total amount of energy that was originally put in.