P1 - Energy Flashcards

1
Q

State the 8 energy stores

A
  • Thermal
  • Kinetic
  • Gravitational potential
  • Elastic potential
  • Chemical
  • Magnetic
  • Electrostatic
  • Nuclear
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2
Q

Description of Magnetic energy store

A

Is the energy stored when repelling poles have been pushed closer together or when attracting poles have been pulled further apart.

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3
Q

Description of thermal energy store

A

In hotter objects, the particles have more internal energy and vibrate faster

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4
Q

Description of Chemical energy store

A

The energy stored in chemical bonds, such as those between molecules

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5
Q

Description of kinetic energy store

A

The energy of a moving object

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6
Q

Description of electrostatic energy store

A

The energy stored when repelling charges have been moved closer together or when attracting charges have been pulled further apart

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7
Q

Description of elastic potential energy store

A

The energy stored when an object is stretched or squashed

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8
Q

Description of gravitational potential energy

A

The energy of an object at height.

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9
Q

Examples of magnetic energy store (3)

A
  • Fridge magnets
  • compasses
  • maglev trains which use magnetic levitation
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10
Q

Examples of thermal energy store

A
  • Human bodies
  • hot coffees
  • stoves or hobs
  • Ice particles vibrate slower, but still have energy
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11
Q

Examples of chemical energy store

A
  • Foods
  • muscles
  • electrical cells.
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12
Q

Examples of kinetic energy stores

A
  • Runners
  • buses
  • comets
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13
Q

Examples of electrostatic energy store

A
  • Thunderclouds,

* Van De Graaff generators

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14
Q

Examples of elastic potential energy store

A
  • Drawn catapults
  • compressed springs
  • inflated balloons
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15
Q

Examples of gravitational potential energy

A
  • Aeroplanes
  • kites
  • mugs on a table
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16
Q

State the 4 energy transfers

A
  • mechanically (by a force doing work)
  • electrically (work done by moving charges)
  • heating
  • radiation (e,g light or sound)
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17
Q

What happens when a system changes

A
  • Energy is transferred
  • It can be transferred into or away from the system
  • Or between different objects in the system or between different types of energy stores
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18
Q

What happens in a graph when energy in given out (exothermic) (and draw it)

A

Downwards around as energy is released

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19
Q

What happens in a graph when energy is taken in (endothermic)

A

An upwards arrow which shows that energy is taken in

20
Q

Conservation of energy principle

A

Energy can be transferred usefully, stored or dissipated but can never be created or destroyed

21
Q

Example of the conversation of energy principle (3)

A
  • A mobile phone is a system
  • When the phone is used, energy is transferred usefully from chemical energy store (battery)
  • But some energy is dissipated to thermal energy store of phone
  • Phone starts to become hot as it is used for a while
22
Q

Dissipated energy

A

No longer useful when it heats the environment

23
Q

Describe energy transfers for closed systems (4)

A
  • A cold spoon is dropped into an insulated flask of hot soup then sealed
  • The flask is a perfect thermal insulator so spoon and soup form closed system
  • Energy transferred from the energy store of soup to the useless thermal energy store of spoon
  • Energy transfers have occurred within the system, but no energy has left the system - net change is zero
24
Q

What happens when energy is transferred between stores

A
  • Not all of the energy is transferred usefully into the store that you want it to go
  • Some energy is always dissipated when an energy transfer takes place
25
Q

Energy transfers in a pendulum

A
  • Gains gravitational potential energy due to increased height
  • When released this energy becomes transferred to kinetic energy
26
Q

Energy transfers in a bungee

A
  • When the person starts to fall freely, it speeds up as it falls
  • The energy transferred from gravitational potential to kinetic energy store
27
Q

What is a closed system

A

Is a system in which no energy transfers take place out of or into the energy stores of the system

28
Q

What is energy measured in?

A

Joules (J)

29
Q

Describe the action of frictional forces on objects and the associated heating effect (3)

A
  • Friction works against the motion and acts in the opposite direction
  • When one object is sliding on another it starts to slow down due to friction
  • By rubbing them together we generate friction and therefore heat
30
Q

Why do objects become heated by frictional forces

A

When friction acts some useful kinetic energy is transferred to dissipated heat energy

31
Q

The formula to work out work done

A

Work done (J) = Force (N) x Distance (m)

32
Q

State the factors which affect the change in the gravitational potential energy store of a system

A
  • The higher an object is lifted the more energy that is transferred to the store
  • The amount of the store depends on mass height and strength of the gravitational field the object is in
33
Q

The effect of gravitational field strength on gravitational potential energy

A
  • The stronger the gravitational field strength the more gravitational potential energy
  • The less gravitational field strength the more gravitational potential energy
34
Q

Equation for gpe

A

Mass (Kg)x gravitational field strength (N/kg) x height (m)

35
Q

Equation for kinetic energy

A

Kinetic energy (j)= 0.5 x mass (kg) x (speed)2 (m/s)

36
Q

Equation for elastic potential (j)

A

0.5 x spring constant (N/m) x (extension)2 (m)

37
Q

Equation for change in thermal energy (j)

A

Mass (kg) x specific heat capacity (J/kg°C) x temperature (°C)

38
Q

The specific heat capacity of a substance

A

Is the amount of energy required to raise the temperature of one kilogram of the substance by one celsius degree

39
Q

Specific heat capacity required practical (7)

A

1) To investigate a solid material (e,g copper) you’ll need a block of the material with two holes in it (for heater and thermometer to go inside)
2) measure the mass then warp in an insulating layer (e,g newspaper) to reduce the energy transferred from the block to the surroundings - the. Insert heater and thermometer
3) measure initial temp - set potential difference of power supply to 10V - turn on the power supply and start a stop watch
4) temp of material may increase - electrical to thermal energy store in power supply
5) take readings of the temp every minute for 10 minutes - should find that current does not change as the block heats up
6) then turn off supply - using P=VI calculate the power supplied to the heater - use this to calculate energy transferred to the heater using (E=Pt)
7) Plot a graph of energy transferred to the thermal energy store of the block against temperature

40
Q

Power

A
  • Is the rate at which energy is transferred

* Or, the rate of doing work

41
Q

Equations for power (2)

A
  • Power (w)= energy transferred (j) divided by time(s)

* Power (w) = work done (j) divided by time(s)

42
Q

Example of power (4)

A
  • It take 8000J of work to lift a stunt performer to the top of a building
  • Motor A can lift the stunt performer to correct height in 50 secs
  • Motor B would take 300secs to lift the performer to the same height
  • Both motors transfer the same amount of energy but motor A would do it quicker than motor B so motor A is the more powerful motor
43
Q

Ways of reducing unwanted energy transfers (2)

A
  • Lubricants - can reduce the friction between objects’ surfaces when they move e,g oil
  • Thermal insulation e,g Cavity walls, loft insulation, double glazed windows, Draught excluders
44
Q

What happens when the thermal conductivity of a material increase

A

The rate of the energy transfer by conduction across the material increases

45
Q

How is the rate of cooling of a building affected by the thickness and thermal conductivity

A

The thicker the walls and the lower the thermal conductivity, the slower the rate of energy transfer will be - the building will cool more slowly

46
Q

Equation for efficiency (2)

A
  • Useful output energy transfer divide by total input energy transfer
  • Useful power output divided by total power input
47
Q

Ways to increase efficiency of an intended energy transfer (4)

A
  • waste less energy
  • insulating objects
  • Lubricating them
  • making them more streamlined