P1 - Energy Stores

What are the main energy stores?

Thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic and nuclear

What happens when a system changes?

Energy is transferred between stores

Give examples of systems and energy changes

• A moving object hitting a wall → kinetic → thermal
  

• A falling object → gravitational potential → kinetic

What is the law of the conservation of energy?

Energy cannot be created or destroyed; it can only be transferred, stored or dissipated

What is the equation for kinetic energy?

Eₖ = ½ × m × v².

What happens to kinetic energy if velocity doubles?

It quadruples

What is the equation for gravitational potential energy?

Eₚ = m × g × h

When does gravitational potential energy increase?

When an object is raised

When does it decrease?

When an object falls

What is the equation for elastic potential energy?

Eₑ = ½ × k × e²

When does elastic potential energy increase?

When a spring or elastic object is stretched or compressed

What is meant by ‘work done’?

The energy transferred when a force moves an object through a distance

What is the equation for work done?

W = F × s

What is the equation linking power, work and time?

P = W ÷ t

What is the equation linking energy transferred, charge and potential difference?

E = Q × V

What is the equation linking power, potential difference and current?

P = V × I

What is the equation linking power, current and resistance?

P = I² × R

What is specific heat capacity?

The amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C.

What is the equation for the change in thermal energy?

Change in thermal energy = Mass x specific heat capacity x temperature change

What is the aim of the SHC practical?

To investigate how the mass of a substance and the energy supplied affect temperature change

What equipment is used?

• A block of the material
  

• Heater
  

• Thermometer
  

• Ammeter
  

• Voltmeter
  

• Power supply
  

• Insulation

How to carry out the practical?

1. Measure the mass of the block using a scale
   

2. Place heater in one hole and thermometer in other hole and wrap the block with insulation
   

3. Connect the heater to a power supply. Put an ammeter in series and a voltmeter in parallel
   

4. Record the starting temperature
   

5. Switch on the power supply and start the stopwatch

SHC practical

6. Record the current and potential difference
   

7. Take readings of the temperature every minute for 10 minutes
   

8. Calculate the power using Power = Current x potential difference (P = I x V)
   

9. Calculate the energy transferred using Energy = Power x time (E = P x t)
   

10. Plot temperature on the y-axis and plot time on the x-axis.
    

11. Use the SHC equation to find out the SHC

How do you calculate the energy supplied?

E = V x I x T (Energy = Voltage x Current x Time)

How can heat loss be reduced?

By using insulation around the block

What happens to useful and wasted energy?

Useful energy is transferred to the desired store; wasted energy is dissipated to the surroundings

How can wasted energy be reduced?

Using lubrication, thermal insulation

What are lubricants?

• Lubricants can be used to reduce the friction between the objects’ surfaces when they move.
  

• They are usually liquids so they can flow easily between objects

What is conduction?

The transfer of heat through a solid by particle vibrations, from a hotter to a cooler area

What is convection?

The transfer of heat in liquids and gases by the movement of particles, forming convection currents

What is the equation for efficiency?

Efficiency = (Useful energy output ÷ total energy input) x 100

What are the main energy resources used in the UK?

Fossil fuels, nuclear fuel, biofuels, wind, tidal, solar and geothermal

What is meant by a renewable energy resource?

A source of energy that can be replenished as it is being used

What are some advantages of renewable energy resources?

• Environmentally friendly
  

• Reduces carbon emissions
  

• Sustainable for the future

What are some disadvantages?

• Unreliable supply
  

• High initial cost
  

• Requires large area of land – loss of habitat (affects wildlife)

What is a non - renewable energy source?

A source of energy that is finite and that will eventually run out

What are some advantages?

• Reliable energy supply
  

• High energy output
  

• Cheap to produce

What are some disadvantages?

• They are finite and will run out
  

• Burning fossil fuels releases carbon dioxide and other harmful gases
  

• Contributes to climate change as greenhouse gases increase global warming

What is a biofuel?

They are renewable energy resources created from plant products or animal dung

What are some advantages?

• Carbon neutral
  

• Lower greenhouse emissions

What are some disadvantages?

• Deforestation – Loss of habitat
  

• Lower energy output
  

• Very expensive to refine bio-fuels