Conservation Of Energy

What is conservation of energy?

• Energy cannot be created or destroyed

• It can only be transferred from one to another

What is energy measured in?

Joules (J)

What are some energy stores?

Chemical energy, kinetic energy, thermal energy, gravitational potential energy, elastic potential energy and nuclear/atomic energy

What are the 5 energy transfers?

Transferred by: forces, electricity, light, heating and sound

What does a sankey diagram look like?

How do you calculate efficiency?

Efficiency = useful energy/total energy supplied

What does gravitational potential energy depend on? (3 things)

• The mass of an object

• How far the object moved upwards

• The strength of gravity (9.8 N/Kg on earth)

What is the equation for gravitational potential energy?

GPE=Mass x gravity x change in height

What is the equation for kinetic energy?

½ x mass x speed²

What are the advantages and disadvantages of natural gas as a non-renewable energy resource?

• Burns cleaner than coal

• Oil is more available

• Fracking to extract gas damages environment

What are the advantages and disadvantages of oil as a non-renewable energy resource?

• Easy to supply to engines

• Oil will run out in the 21st century

• Oil spills are very damaging to the environment

What are the advantages and disadvantages of nuclear power as a non-renewable energy resource?

• Does not produce carbon dioxide or pollution

• Very safe

• Power stations are expensive to maintain

• Damaging accidents can spread radiation for hundreds of miles

• Nuclear waste is buried and takes thousands of years to be safe again

What are the advantages and disadvantages of coal as a non-renewable energy resource?

• Easy to store and transfer

• Very safe to use in homes and power stations

• Released carbon dioxide

• Mining coal creates a lot of pollution

Where does solar energy come from?

Heat and light from the sun

How is solar energy transferred into a useful store?

Light is absorbed and turned into electric energy and can heat water

What are the advantages and disadvantages of solar energy as a renewable energy resource?

• Renewable and no pollution

• Expensive

• Only works when sunny

Where does energy created by wind come from?

Kinetic energy from wind turbines

How is kinetic energy made by wind turbines transferred into useful energy?

The kinetic energy is transferred into electrical energy

What are the advantages and disadvantages of wind turbines as a renewable energy resource?

• Cheap and no pollution

• Not visually appealing and noisy

• Has to be windy

• Threatens wildlife

Where does tidal energy come from?

Tides

How is energy from tides transferred into a useful energy?

The gravitational potential energy produced can be transferred to electrical energy

What are the advantages and disadvantages of energy produced by tides as a renewable energy resource?

• Reliable

• Cheap once built

• Local flooding

• Landlocked countries can’t access it

• Can disrupt the ocean

Where does geothermal energy come from?

The Earth’s rocks

How is geothermal energy transferred into a useful store?

Heat energy is made into electrical energy

What are the advantages and disadvantages of geothermal energy as a renewable energy resource?

• No pollution

• environmentally safe

• Very few places do this

• Money needed to drill deep

• Vulnerable to earthquakes

Where does hydroelectric energy come from?

It comes from rivers and dams

How is hydroelectric energy transferred into a useful store?

The kinetic energy produced is transferred to electrical energy

What are the advantages and disadvantages of hydroelectric energy as a renewable energy resource?

• No pollution

• Lots of money

• Damages environment

Where does wave energy come from?

Energy from waves can be used by machines

How is wave energy transferred into useful energy?

The kinetic energy is transferred into electrical energy

What are the advantages and disadvantages of wave energy as a renewable energy resource?

• No pollution

• Lots of machines

• Expensive

• Damaged by natural disasters

Where does biomass energy come from?

Chemical potential energy in things that were alive can be turned into heat energy

What are the advantages and disadvantages of biomass energy as a renewable energy resource?

• No special equipment needed

• Doesn’t contribute to global warming

• Large areas needed

Whare are the different energy stores and some examples of them?

• Chemical- fuel, food battery

• kinetic- moving objects

• gravitational potential energy- raised mass

• elastic- stretched object

• thermal- hot object

• magnetic- two magnets

• electrostatic- two charges

• nuclear- radioactive decay

What is a closed system?

In a closed system, where no energy is added and none can escape, the total energy in that system must remain constant

How can energy be transferred from one store to another?

• Mechanically- by a force moving through a distance

• Electrically- by the use of an electric current

• Thermally- because of a difference in temperature

• Radiation- by waves such as light or sund

What happens to energy when it is transferred from one store to another?

Some energy will be usefully transferred, some will be wasted and some with be dissipated

When do mechanical processes become wasteful?

When they lead to a rise in temperature of the surrounding through heating (Unless that is what they were made for)

What does the rate of thermal energy transferred through the wall of a house depend on?

• The difference in temperature between the warmer interior and the colder exterior

• The thickness of the walls

• The materials the walls are made from

What do all machines do when transferring energy?

They waste some of the energy they transfer. Most waste energy as heat

How can unwanted energy transfers be reduced?

Thermal insulation and lubrication

What does it mean if a material has a high thermal conductivity?

It is a better conductor of energy

What is the equation for the efficiency of a device?

Efficiency= useful energy/total energy x 100

What was the most major source of fuel before 1900?

Wood

What kind of fuels have been more used in recent years?

Nuclear and hydroelectric

Why can we not use fossil fuels forever?

They will eventually run out and we can't keep using it at the rate we are using them

What does the greater use of fossil fuels cause?

It will lead to more carbon dioxide released into the atmosphere and there will greater global warming leading to sever weather, flooding and threats to food supplies

What is gravitational potential energy?

The energy possessed by a body due to it’s height above the Earth

What does the value of gravitational potential energy depend on?

• The mass of the body

• The gravitational field strength

• The height the body is raised

What is the equation for gravitational potential energy including mass, gravitational field strength and height?

Change in GPE (J) = mass (Kg) x Change in gravitational field strength (N/kg) x Change in vertical height (m)

What is kinetic energy?

Energy stored in moving objects

What is the equation for kinetic energy involving mass and speed?

Kinetic energy (J)= ½ x mass x v²

What two things is kinetic energy directly proportional to?

• The mass of a moving object, doubling the mass doubles the kinetic energy

• It is directly proportional to the square of the speed