P1 - Energy Stores✔️

Question 1

Explain what a chemical energy store is? List some examples?

Answer 1

is the energy transferred during chemical reactions - stores include fuels, food or chemicals found in batteries

Question 2

Explain what a kinetic energy store is?

Answer 2

Describes the energy an object has due to its movment

Question 3

Explain what a gravitational potential energy store is?

Answer 3

used to describe the energy stored in an object because of its position such as an object above the ground

Question 4

Explain what an elastic energy store is?

Answer 4

Describes the energy stored in a springy object when you stretch or squash it

Question 5

Explain what a thermal energy store is?

Answer 5

Decribes the energy a substance has because of its temperature

Question 6

Explain what happens when an electric kettle is used to boil water - refer to energy stores?

Answer 6

The current in the kettle’s heating element transfers energy to the thermal energy store of the water and kettle - which heats up the water

Question 7

Explain what happens when a object is thrown into the air - refer to energy stores?

Answer 7

When an object is thrown into the air the object slows down as it goes up because energy is transferred from the objects kinetic energy store to its gravitational potential energy store and when the object starts to fall freely the force of gravity causes energy to be transferred from its gravitational potential store to its kinetic energy store

Question 8

What is a closed system?

Answer 8

A system in which no energy transfers take place out of or into the energy stores of the system - energy can be transferred between energy stores within a closed system but the total energy of the system is always the same before and after such transfers

Question 9

What does the conservation of energy state?

Answer 9

Energy cannot be created or destroyed

Question 10

Can energy be transferred between stores within a close system?

Answer 10

Yes energy can be transferred between energy stores within a closed system but the total energy of the system is always the same before and after such transfers

Question 11

Explain why the exmaple of a pendulum in a vacuum is a closed system?

Answer 11

Because there is no air resistance acting on it and so no energy would be transferred from any of its energy stores and it would keep swining for ever

Question 12

Give 4 examples of energy transfers?

Answer 12

• waves
• heating
• electric current
• mechanical

Question 13

What does energy transfer equal?

Answer 13

Energy transferred = work done

Question 14

Equation for change of gravitational potential energy store?

Answer 14

Change of gravitational potential energy = mass x gravitational field strength x change of height

Question 15

Define useful energy?

Answer 15

Is energy transferred to where it is wanted in the way that is wanted

Question 16

Define wasted energy?

Answer 16

Is the energy that is not usefully transferred

Question 17

What happens when energy is dissipated?

Answer 17

Whenever energy is transferred for a purpose in any system, some of the energy is transferred usefully and the rest may be stored in less useful ways - this is described as wasted energy

Question 18

Explain how energy is dissipated when using a phone?

Answer 18

When you use the phone energy is transferred from the chemical energy store to the battery in the phone - but some of the energy is dissipated in this transfer to the thermal energy store which heats the phone up

Question 19

Equation for efficiency?

Answer 19

Efficiency = useful ouput energy transferred / total input energy supplied

Question 20

How can you improve efficiency of energy transferred?

Answer 20

By insulating objects, lubricating them and making them more streamlined

Question 21

Why are electric heaters an exception and usually 100% efficient?

Answer 21

Usually all the energy in the electrostatic energy store is transferred to “usefull” thermal energy stores

Question 22

Why is no device 100% efficient?

Answer 22

Wasted energy is usually transferred to useless thermal energy stores

Question 23

Why do machines waste energy?

Answer 23

Due to friction between their moving parts, air resistance, electric resistance and noise

Question 24

Relationship between power and an appliance?

Answer 24

The more powerful and appliance is, the faster the rate at which it transfers energy - power is measured in watts (W)

Question 25

Value of 1 watt?

Answer 25

1 joule