Energy and Heat

Energy

Energy is a quantity that causes something to happen. Energy can be stored, transformed or transferred, but cannot be created or destroyed

7 Forms of Energy - with examples

Energy can either be stores as Potential Energy or can be in a form of motion - Kinetic energy

1. Kinetic Energy - Moving Car

2. Gravitational Potential - Plane

3. Chemical Energy - Gasoline

4. Elastic Energy - Stretched Rubber band

5. Nuclear Energy - Nuclear Reactor

6. Electrostatic Energy - Charged Balloon

7. Thermal Energy - Hot coffee

Energy Transfers

Energy is transferred between stores through different energy transfer pathways

Examples:

Heat Transfer: A stove burner transferring heat to a pot of water. 

Conservation of Energy

In any Energy transfer, the total amount of energy before and after the transfer is constant(energy can’t be destroyed or created). In most energy transfers more than one type of energy is produced. This often means that energy is wasted- not all the energy is transferred to the useful form.

Wasted Energy- wasted in which 2 main ways?

Energy is normally wasted in two main ways: Heat- eg: Bulb, Sound- eg: Fans

The wasted energy is transferred to a form that is not useful, eg: laptop heat

Energy Efficiency -formula

Efficiency refers to how much energy is transfer - not how quickly

Efficiency = (Useful Energy Output / Total Energy Input) x 100%. - for the efficiency as a percentage

Kinetic Energy

Kinetic Energy is basically movement energy

Energy is Measure in Joules(J)

where m is mass, v is velocity.

Formula: KE = 1/2 x m x v²

Gravitational Potential Energy - Formula

Formula: Mass x field strength x change in height

Work

Mechanical and electrical work done is equal to the energy transferred

The force must be in the same direction as the distance moved

Formula : Work = force x distance moved

Power

Power is the work done per unit of time and also as energy transferred per unit of time

Formula:

How forms of energy be obtained from fossil fuels

Fossil fuels are hydrocarbons compounds of hydrogen and carbon. When they are burnt, they combine with oxygen from the air and energy is released as heat

How forms of energy be obtained from Water-tides

Most of the energy of winds is transferred to the sea as wave, which are formed by friction between the wind and the water, the kinetic energy of the waves can turn a turbine to generate electricity

How forms of energy be obtained from Geothermal Resources

The interior of the Earth is hot. Hot rock if found at a shallow depth below Earths surface. They’re hot due to the radioactive substances. Water is pumped down to the hot rock where it boils, and high pressure steam returns where it can be used to make electricity

How forms of energy be obtained from Nuclear Fuels

Inside a nuclear reactor a fast decay of radioactive materials such as uranium. Release the energy they store this is called nuclear fission

How forms of energy be obtained from heat and light energy from the sun

The sun rays shine on solar panels, the solar cells absorb the energy of the rays, and electricity is produced

How forms of energy be obtained from Wind energy

The sun heats ups some parts of the atmosphere more than others. Heated air expands and starts to move around- this is a convection current. This is the origin of winds

A wind turbine converts the kinetic energy of moving air (wind) into electrical energy

Advantages of Solar

• Renewables

• Useful in remote locations

• no fuel costs

Disadvantages of Solar

• Unreliable - Sunlight can drop

• Expensive

Advantages of Nuclear

Provides lots of energy from small mass of fuel

Disadvtages of Nuclear

• Not renewable

• Waste is radioactive

Advantages of Fossil Fuels

• Produce a large amount of energy

Disadvantages of Fossil Fuels

• Not Renewable

• Releases Carbon Dioxide

Advantages of Hydro

• Renewable

• Safe, Clean

Disadvantages of Hydro

• Expensive

Advantages of Wind

• Renewable

Disadvantages of Wind

Unreliable- Speed of wind can change

Expensive

Advantages of Geothermal

• Renewable

Disadvantages of Geothermal

• Only available in a few places on Earth

Using Energy resources of Generate Electricity - Thermal into electricity

The thermal energy produced when fossil fuels are burnt or when nuclear fission takes place is used to heat water in a boiler to form steam. The steam turns the blades of a turbine, transferring thermal energy into kinetic energy. The turbine is linked by an axle to a generator where a voltage is induced in conducting wires when they move in a magnetic field.

Those energy resources that do not use a fuel, such as wind, waves and tides, will not need a boiler,

Pressure of a gas

Pressure of a gas is the force exerted by particles colliding with surfaces, creating a force per unit squared

Particles effect on pressure of gas when temperature changes

If the temperature of the gas is increased, particle will move faster and therefore more collision so the gas will exert a higher pressure

When temperature is decreased pressure decreases

Particles effect on pressure of gas when volume of container changes

When the volume of the container Decreases the. the gas is compressed into a smaller volume, the number of gas particles hitting the sides of the container will increase therefore the pressure increases.

If the pressure Increases the pressure decreasesj

Evaporation

Evaporation is the escape of more energetic molecules from the surface of a liquid

Evaporation causes cooling of a liquid

Evaporation causes cooling of a liquid