Energy

Question 1

8 stores of energy?

Answer 1

1. Kinetic
2. Thermal
3. Chemical
4. Nuclear
5. Elastic Potential energy
6. Gravitational Potential Energy
7. Magnetic
8. Electrostatic

Question 2

Energy must be transferred to do what?

Answer 2

Work

Question 3

What are the 4 ways to transfer energy?

Answer 3

1. Radiation
2. Electrically
3. Mechanically
4. Heat

Question 4

Where does the earths energy come from?

Answer 4

The sun - transferred by radiation

Question 5

Definition of transfer by radiation?

Answer 5

When energy is transferred as sound, light (not touching anything) - not electrically, mechanically or by heating :)

Question 6

Definition of energy transferring electrically?

Answer 6

When energy is transferred through currents

Question 7

Definition of transfer by heating?

Answer 7

When energy is transferred as objects heat up

Question 8

Definition of mechanical transfers of energy?

Answer 8

When energy is transferred by parts moving

Question 9

Law of Conservation of energy?

Answer 9

Energy cannot be created or destroyed, only transferred from one type to another

Question 10

What is energy measured in?

Answer 10

Joules

Question 11

What is work?

Answer 11

Energy transferred

Question 12

equation for work done =

Answer 12

work done (J) = force (N) * distance (m)

Question 13

Weight =

Answer 13

weight (N) = mass (Kg) * gravity (9.8 n/kg)

Question 14

GPE =

Answer 14

GPE (J) = (mass (Kg) * gravity(9.8 n/kg) - weight) * height (m)

Question 15

KE =

Answer 15

KE (J) = 0.5 * M (Kg) * (v*v) (m/s)

Question 16

EPE =

Answer 16

EPE (J) = 0.5 * k (N/M) * (x*x) (M)

Question 17

What happens when a system changes?

Answer 17

Energy is transferred

Question 18

What is a system?

Answer 18

A single object or group of objects of interest

Question 19

What is a closed system?

Answer 19

A system in which neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero.

Question 20

Work can be done when (2) ?

Answer 20

1. Current flows

2. Force moves an object

Question 21

What is kinetic energy?
How can you increase the KE of an object?
When is KE transferred to and away from an object?

Answer 21

Anything that moves has kinetic energy
Increasing an objects mass or speed increases KE
When an object speeds up, KE is transferred to this store, when an object slows down, KE is transferred away

Question 22

What is GPE?
How can you increase the GPE of an object?
When is GPE transferred to and away from an object?

Answer 22

GPE is energy an object has based on its position above the earths surface
Increasing the objects mass, height, or the strength of the gravitational field the object is in increases its GPE
The higher an object is lifted, the more energy is transferred to the store, the more the object is lowered, the more GPE transfers away from the store

Question 23

What is EPE?

How can you increase the EPE of an object?

Answer 23

Elastic potential energy is energy stored as a result of applying a force to deform (stretch/squash) an elastic object
EPE is dependant on the length the object is stretched and the spring constant

Question 24

What does efficiency tell us?

Answer 24

It tells us how much of the energy put in is transferred usefully

Question 25

Efficiency =

Answer 25

efficiency(%) = useful energy output/total energy input* 100 note - efficiency equation can be done in terms of power useful power output (W) / total power output (W) * 100

Question 26

What is Power?

Answer 26

Power is how much work is done per second - measure in Watts

Question 27

Power =

Answer 27

Power (W) = work (J) / time (S)

Question 28

1 W =

Answer 28

1 J per second

Question 29

What is useful energy?

Answer 29

Energy transferred to where it is wanted in the way it is wanted

Question 30

What is wasted energy?

Answer 30

Energy that is not usefully transferred

Question 31

Energy that is not transferred usefully is...

Answer 31

dissipated

Question 32

Why do devices waste energy? (4)

Answer 32

1. Friction between moving parts causes heating 2. The resistance of a wise causes the wire to get hot when current passes through it 3. Air resistance causes a force on a moving object that opposes its motion 4. Sound created by machinery causes energy transfer to the surroundings

Question 33

How to reduce wastes of energy (4)?

Answer 33

1. Lubricate moving parts to avoid friction 2. Uses wires in circuits with as little electrical resistance as possible 3. Streamline objects to reduce air resistance 4. Cut out noise by tightening loose parts for example

Question 34

energy changes when an is object projected upwards

Answer 34

Energy of the object starts of by being stored as kinetic energy, it slows down as it increases in height because the KE is transferred to GPE

Question 35

energy changes when an moving object hits an obstacle

Answer 35

energy shifts from kinetic store of object to the thermal energy store of object and obstacle

Question 36

energy changes when an object accelerates at a constant force

Answer 36

energy shifts from chemical store of the fuel to the kinetic store of the object

Question 37

energy changes when a object slows down

Answer 37

energy shifts from the kinetic store of the vehicle to the thermal store of the brakes and surroundings

Question 38

energy changes when bringing water to boil in an electric kettle

Answer 38

energy shifts from chemical store (in the electricity) to the thermal store of the water

Question 39

Light bulb useful energy and wasted energy?

Answer 39

useful: light emitted from the glowing filament wasted: energy transferred from the filmet heating the surroundings

Question 40

Electric heater useful energy and wasted energy?

Answer 40

useful: Energy heating surroundings wasted: Nothing really (some light emitted from glowing element)

Question 41

Electric toaster useful energy and wasted energy?

Answer 41

useful: energy heating bread wasted: energy heating the toaster case and surrounding air

Question 42

Electric kettle useful energy and wasted energy?

Answer 42

useful: Energy heating water wasted: Energy heating kettle itself

Question 43

Hairdryer useful energy and wasted energy?

Answer 43

useful: kinetic energy of air driven by fan and energy heating air flowing past heating element wasted: Sound of fan motor energy heating hairdryer itself

Question 44

Electric motor useful energy and wasted energy?

Answer 44

useful: kinetic energy of objects driven by motor, GPE potential energy of object lifted by motor wasted: energy heating the motor and energy transferred as sound

Question 45

What is the spring constant? What is extension?

Answer 45

The spring constant, k, is a measure of the stiffness of the spring - the higher the k, the stiffer the spring The increased length of an object when stretched is the extension, it is equal to: new length - original length

Question 46

What is the limit of proportionaltiy?

Answer 46

The limit of proportionality refers to the point beyond which Hooke's law is no longer true when stretching a material. The elastic limit of a material is the furthest point it can be stretched or deformed while being able to return to its previous shape. Once a material has gone past its elastic limit, its deformation is said to be inelastic.