P2 - Energy

Question 0

Law of conservation

Answer 0

Energy cannot be created or destroyed, only transferred

Question 1

What is energy measured in ?

Answer 1

Joules and kilojoules

J or KJ

Question 2

Chemical store

Answer 2

Food, fuels, batteries

Example : chocolate

Question 3

Thermal store

Answer 3

Hot objects

Example : the sun

Question 4

Kinetic store

Answer 4

Moving objects

Example : walking person

Question 5

Gravitational potential store

Answer 5

Position in a gravitational field (anything above ground has gravitational potential energy)
Example : ski lift

Question 6

Elastic store

Answer 6

Changing shape, stretching, squashing

Example : rubber band

Question 7

Electric energy

Answer 7

Anything that has a flowing current, had electrical energy

Question 8

Light energy

Answer 8

Anything luminous gives off light energy

Example : torch, light bulb

Question 9

Sound energy

Answer 9

Anything noisy gives off sound energy

Example : instruments

Question 10

Process of conduction

Answer 10

Conduction happens best in solids (even better in metals) because of the free electrons. When particles gain thermal energy, they vibrate more, causing them to collide with the particles next to them, transferring energy. This transfer of energy continues, until the two surfaces are at the same temperatures (energy) - equilibrium

Question 11

Process of convection

Answer 11

Particles with a lot of heat energy in a liquid or gas move, and take the place of particles with less heat energy. Particles in hotter less dense areas (deser because the particles are further apart), move faster than those in cooler areas. The hotter, denser particles rise, and cooler denser particles take their place.

Question 12

When can heat be transferred

Answer 12

Only when there is a temperature difference

Question 13

Insulator

Answer 13

An object that does not conduct energy well

Question 14

Good insulators :

Answer 14

Rubber
Wood
Plastic
Bubble wrap

Question 15

Why is a material such as bubble wrap a good insulator

Answer 15

Bubble wrap is a good insulator because it is made of small pockets of air, and because the particles in air are very spread out, it takes longer for the energy/heat to be transferred through it, making it a good insulator.

Question 16

Good conductors:

Answer 16

Metal

Question 17

Why are non metals good insulators ?

Answer 17

Because energy can only be transferred slowly via the vibration of particles about a fixed position

Question 18

What is IR ?

Answer 18

IR is a type of electromagnetic radiation, which transfers energy through waves rather than particles, meaning that it can travel through a vacuum. IR can be detected by the skin etc, and an example source of IR is sunlight

Question 19

Black Matt

Answer 19

• absorbs most heat

- good absorber of IR

Question 20

Black materials

Answer 20

Absorb heat as its dark

Good absorber of IR

Question 21

White materials

Answer 21

Absorb less heat

Good reflector of IR

Question 22

Shiny materials

Answer 22

Poor absorber of heat

Good reflector

Question 23

Formula of power

Answer 23

Power = Energy transferred
———————
Time taken

Question 24

Energy used formula

Answer 24

Energy = power x time

Question 25

Cost of electricity formula

Answer 25

Cost = number of kWh x cost per kWh

Question 26

Work done equation

Answer 26

Work done = force x distance

J = N x M

Question 27

Difference between heat and temperature.

Answer 27

Heat is a from of energy and temperature is the measurement of that energy.

Question 28

Difference between energy and power

Answer 28

Energy is the capacity to do work whereas power is the rate at which this work is done.

Question 29

Examples of IR

Answer 29

Sun light
A lamp
A fire

Question 30

What is a simple machine ?

Answer 30

A simple machine is a machine that makes it easier to lift things. It reduces the force that you need to do a job, or increases the distance that something moves when a force is applied.

A lever is a simple machine eg. putting a screwdriver between the lid and rim of the tin, allows you to open the with a much smaller force. The force applied to the lever is bigger than the forever that you apply with just your hand, making a lever a force multiplier. Energy is conserved because the distance the lid is moved up is smaller than the distance moved by your hand.

A gear system is another simple machine. You can use a gear system to increase the force, change direction, or go faster. When the cog at the back of a bicycle is smaller it takes less force to turn it. It is a force multiplier.

Question 31

How does an electro magnet work ?

Answer 31

1. A simple motor contains a coil of wire and permanent magnets
2. Current flows through the coils
3. The coil becomes an electromagnet
4. The forces between the electro magnet coil and permanent magnets make the coil spin.