Physics - Energy

- Thermal

- Kinetic

- Gravitational Potential

- Elastic Potential

- Chemical

- Magnetic

- Electrostatic

- Nuclear

When energy is transferred to an object, the energy is stores in one of the objects energy stored.

Energy can be transferred mechanicallly, electrically, by heating or by radiation. 

A system is another word for a single of a group of objects

When a system changes, energy is transfereed - It can be transferred to or away from the system, between different objects or between different types of energy stores.

Closed System:

- a system where neither energy nor matter can enter or leave

- the net charge in the total energy of a closed system will always be 0

Heating:

- Energy can be transferred by heating

- Example: when you boil a kettle energy is transferred electrically to the thermal energy store of the kettles heating element, which transfers energy by heating to the waters thermal energy store.

Doing Work:

- Work Done is the same as saying energy transferred 

-  Work can be done when current flows or by a force moving an object

Initial Force:  The initial force exerted by a person to throw a ball upwards does work.

- It causes an energy transfer from the chemical energy store of the persons arm to the kinetic energy store of the ball and arm.

Gravitational Potential Force:  A ball dropped from a height is accelerated by gravity - the gravitational force does the work.

- It causes It cases energy to transferred from the balls grav pot energy store to its kinetic energy store.

Friction: The friction between a car's brakes and its wheels does work as it slows down.

- It causes an energy transfer from the whells' kinetic energy stores to the thermal energy store of the surroundings.

Stationary Object: In a collision between a car and a stationary object, the normal force between the car and the object does work.

-It causes the energy to be transferred from the cars kinetic energy store to other energy stores e.g. elastic potential energy

- Anything that is moving has energy in its kinetic energy store - energy is being transferred to this store when an object speeds up.

- Energy is transferred away from this store when an obejct slows down.

- The energy in the kinetic energy store depends on the objects mass and speed, the greater the mass and speed the more energy will be in its kinetic store. 

Formula:

kinetic energy = 1/2 * mass * speed^2

Raised Obejcts:

- Lifting an object in a gravitational field requires work - this causes a transfer of energy to the gravitational potential energy store of the raised object.

The amount of energy in this store depends on the objects mass, height and strength of he gravitaional field the object is in

Formula:

GPE = mass * grav field strength * height

Falling Objects:

- When something falls energy is transferred from its grav pot energy store to its kinetic energy store.

- If there is air resistance (there almost always is) Some will be transferred to other store e.g. thermal (friction)

- More energy needs to be transferred to the thermal energy store of some materials to increases the temperature than others.

- Specific Heat Capactity is the amount of energy needed to raise the temperature of 1KG of a substance by 1^c

Formula:

change in thermal energy - mass * shc * temperature change

1 - for a solid you need a block (e.eg. copper) with 2 holes in 

2 - measure the mass of the block and wrap it in a layer of insulation - insert the thermometer and heater

3 - Measure the initial temp and set the potential difference to 10v - turn on power supply and start stopwatch

4 - current does work on the heater transferrign energy elecrically from the power supply to the heaters thermal energy store. 

5 - take readings of the termperature and current every minute for 10 minutes

6 - current shouldn't change turn off power supply using current find the power supplied and energy transferred.

7 - plot graph of time against energy transferred - find the gradient - shc = 1/gradient*mass of block

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

When energy is transferred between stores not all of the energy is transferred usefully - some energy is always dissipated (lost to the surroundings) 

Dissipated energy can also be called wasted energy 

- Power is the rate of doing work / rate of energy transfer

- Power is measured in watts 

- A powerful machine is one which transfers a lot of energy in a short space of time

Formula:

- energy transferred/time

- workd done/time

Conduction is the process where vibrating particles transer energy to neighbouring particles

1 - energy transferred to an object by heating is transferred to the thermal energy store of the object - this energy is shared across the kinetci energy stores of the particles in the object.

2 - the particles in the part of the onject being heated vibrate more and collide with each other. These collisions cause energy to be transferred between particles kinetic energy stores

3 - This process continues throughout the object until the energy is transferred to the other side of the onject then its usually transferred to the surroundings.

4 - Thermal conductivity is a measure of how quickly energy is transferred through a material in this way. Materials with a high thermal conductivity transfer energy between their particles quickly. 

Where energetic particles move away from hotter to cooler regions

1 - convection can happen in gases and liquids. Energy is transferred by heating to the thermal store of the liquid or gas - this energy is shared across the kinetic energy stores of the gas or liquids particles.

2 - Unlike solids, the particles in liquids and gases are able to move - when you heat the particles they move faster and the space between individual particles increases - this causes the density to decrease

3 - because liquids and gases can flow, the warmer and less dense region will rise above denser cooler regions. If there is a constant heat source, a convection current can be created. 

Radiators: energy is transferred from the radiator to the nearby air particles by conduction, the air by the radiator becomes warmer and less  dense and rises above being replaced by cooler air. At the same time the previously heated air transfers energy to the surroundings therefore cooling and sinking. The cycle repeats = convection current.

Lubrication: Whenever something moves, there is usually at least on rictional force acting against it - this causes some energy to be dissipated 

Air resistance can transfer energy froma falling objects kinetic energy store to its thermal e store

Lubricants can be used to reduce the friction between objects surfaces when they move (usually liquids so they can flow easily and coat the object)

Insulation: Insulation helps prevent energy losses through heating.

- thick wall that are made from a material with a low thermal conductivity, the thicker the walls and the lower their thermla conductivity, the slower the rate of energy trasnfer will be.

- loft insulation

- double-glazed windows 

- draught exculders

1 - Boil water in a kettle - pour some of it into a sealable container and measure mass of water

2 - Use a themometer to measure the initial temperature of the water

3 - Seal the container and leave it for 5 minutes - use a stopwatch

4 - remove lid and measure final temperature of the water

5 - Pour away the water and allow the container to cool and room temperature

6 - Repeat the experiment but wrap the container in a different material but use the same mass of water.

- The lower the temperature difference the better the material is as a thermal insulator

- You could also investigate how the thickness of the material affects the thermal insulator it is.

1 - each turbine has a generator inside it - the rotating blades turn the generator and produce electricity 

2 - there is no pollution

3 - they can be noisy

4 - high initial costs but no fuel costs and minimal running fees

5 - when there is no wind or the wind is too strong there can be problems

Solar Cells: Solar cells generate electric currents directly from sunlight - usually best source of energy to charge batteries in calculators and watches - dont use a lot of electricty 

Often used in remote places to power electric road signs and satellites - no pollution and in sunny countries. 

You can't increase the power output when ther is extra demand - high initial costs but small scale

Geothermal Power: 

This is only possible in volcanic areas where hot rocks lie close to the surface - the source of much of the energy is the slow decay of various radioactive elements such as uranium.

It is free, reliable energy that does very little damage to the earth

Geothermal Energy can be used to gnerate electricity or to directly heat buildings

However there aren't many suitable locations and the cost of building a plant is high in comparison to the amount of energy it produces. 

Hydro-electric:

1 - usually requires the flooding of a valley by building a big dam - water is allowed out through turbines (it doesn't create pollution)

2 - There is a big impact on the enviroment due to the flooding of a valley - many animals homes are destroyed, also look very unsightly 

3 - can provide an immediate response to an increased demand for electricity - only unreliable in droughts - high initial costs

Wave: 

1- You need lots of small wave powered turbines located around the coast like wind turbines

2 - No pollution but can be very unreliable, waves die out when winds drop

3 - High initial costs but no fuel costs and minimal running costs, can't provide lots of energy

Tidal Barrages: 

1 - Tidal barrages are big dams built across river estuaries with turbines in them - the water is allowed out through turbines at a controlled speed

2 - Tides are produced by the gravitational pull of the moon and sun

3 - No pollution but can destroy the habitas of animals and destroy the view

4 - They are fairly reliable they are regular however the height is varied 

5 - High initial start up costs but no fuel costs

1 - Bio-fuels are renewable energy resources created from plant products or animal dung - they can be solid liquid or gas and can be burnt to produce electricity (like fossil fuels)

2 - They are supposedly carbon neutral - but in order for this to be true you have to be planting things at the same rate you are burning them

3 - fairly reliable only take a short time to grow - but cannot respond to immediate energy demands.

4 - the cost to refine bio-fuels is very high and there are worries that there isnt enough space to grow crops for food as well as bio-fuels.

Non-Renewables: Fossil fuels and nuclear energy are reliable however whilst there are plenty available at the moment they are slowly runnign out. 

They have serious enviromental effects - they release co2 into the atmosphere, this adds to the greenhouse effect which contributes to global warming. Also releases sulfur dioxide which causes acid rain (harmful to trees and soils). Coal mining makes a mess of the landscape, oil spillages damage enviroments, nuclear waste is very dangerous and difficult to dispose of.