physics

Respiration is the chemical process of releasing energy from organic compounds.

• Aerobic respiration - the breakdown of the molecule with oxygen. This releases lots of energy. the cell needs to possess mitochondria.
• Anaerobic respiration -The breakdown of the molecule without oxygen. This releases much less energy.
• equation for respiration:

ATP (adenosine triphosphate) is a small molecule with 3 phosphate groups.

During respiration, Lower energy bonds are formed and the difference is released and used to attach a P to sdenosine-P-P (ADP adenosine diphosphate), making ATP.Energy is released when one of its phosphate groups breaks off from the molecule. ATPase (adneosine triphosphatase) is the enzyme that breaks down ATP.

When energy is required at a later time by a cell, it can use the ATP and break a P off the end. This releases the energy needed. The more ATPs used, the more energy is released.

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• the more powerful an appliance, the faster the rate at which it transfer energy.
• kinetic energy: is an energy on motion. equation:
• ¹⁄₂ × mass×  speed²
• potential energy=mass(m)×gravity(g)×height(h)
• work done= force/ distance
• power=energy/time
• efficiency=useful energy/total energy
• cost=power×time×cost per unit

• conduction is the transfer of heat between substances through direct contact. cooper, steel, iron are good conductors. while paper, air,foam are poor conductors
• when a metal rod is heated at one end , the free electrons at the hot end gain kinetic energy and move faster.
• these electrons diffuse and collide with other freee elctrons and ions in the cooler partts of the metal.

• convection is the up and down movement of liquid and gas. it happens when fluid is heated due to circulation.
• as the liquid or gas is heated, it warms, expands and rises because it is less dense. When the gas or liquid cools, it becomes denser and falls. As the gas or liquid wams and rises, or cools and falls, it creates a convection current.

• Radiation is when an electromagnetiv waves travel through space. when it comes in contact with an object, it transfer heat.
• dark surfaces are better at absorbing heat. heaters are painted white because the radiation reflected from the shiny surface travels and gives out heat.

• insulators do not let electrons flow very easily from one atom to another. Insulators are materials whose atoms have tightly bound electrons. These electrons are not free to roam around and be shared by neighboring atoms. e.g glass, plastic, rubber, air, and wood.
• A U value is a measure of heat loss in a building element such as a wall, floor or roof. 

u-value= heat loss/ area* temperature

change the kw to watts. multiply by 1000

Heat energy is transferred from homes through the

• roof (conduction, radiation)
• walls (conduction, radiation)
• floor (conduction)
• windows (conduction, convection, radiation))
• doors (conduction & convection)

Heat loss through windows can be reduced using double glazing. There may be air or a vacuum between the two panes of glass. Air is a poor conductor of heat, while a vacuum can only transfer heat energy by radiation.

Heat loss through walls can be reduced using cavity wall insulation. This involves blowing insulating material into the gap between the brick and the inside wall, which reduces the heat loss by conduction. The material also prevents air circulating inside the cavity, therefore reducing heat loss by convection.

Heat loss through the roof can be reduced by laying loft insulation. This works in a similar way to cavity wall insulation.

momentum is mass in motion

equation for change in momentum:

Force = change in momentum/time taken

P = m× v

Units: kgms^-1 or Ns

conservation of momentum : momentum before collision equals to the momentum after collision.

pay-back time in years  =  cost of energy-saving measure  ÷  money saved each year

Example

Double-glazing might cost £2,500 to install and save £100 a year in fuel bills. What is the pay-back time?

pay-back time = cost of energy-saving measure ÷ money saved each year 
= 2,500 ÷ 100 
= 25 years

1. The coal is burned in a boiler which causes the water in the boiler pipes to become steam.
2. The steam travels through the pipes to the turbine.
3. The steam spins the turbine blades.
4. The spinning blades turn a shaft connected to the generator.
5. In the generator, big magnets spin close to coils of wire.
6. When this happens, electrical current is produced in the wires.
7. Then the electricity goes out through wires to homes, schools, and businesses.

 Advantages of Fossil Fuels

• A major advantage of fossil fuels is their capacity to generate huge amounts of electricity in just a single location. 

• Fossil fuels are very easy to find. 

• they are very cost effective. 

Disadvantages of using fossil fuels

• Their supply is limited and they will eventually run out. 
• Fossil fuels release carbon dioxide when they burn, which adds to the greenhouse effect and increases global warming. 
• Coal and oil release sulfur dioxide gas when they burn, which causes breathing problems for living creatures and contributes to acid rain.

Hydroelectric power (HEP)

hydroelectric power stations use the kinetic energy in moving water. But the water comes from behind a dam built across a river valley. The water Behind the dam contains gravitational potential energy. This is transferred to kinetic energy as the water rushes down through tubes inside the dam. The moving water drives electrical generators, which may be built inside the dam.

Advantages

• It is a renewable energy resource and there are no fuel costs. 
• No harmful polluting gases are produced. 
• very reliable and can be turned on quickly.

Disadvantages

•  Destroy the habitat of species
• Hydroelectricity dams flood farmland and push people from their homes. 
• The rotting vegetation underwater releases methane, which is a greenhouse gas.

• Solar panels do not generate electricity,they heat up water. They are often located on the roofs of buildings where they can receive heat energy from the sun.
• A pump pushes cold water from the storage tank through pipes in the solar panel. The water is heated by heat energy from the sun and returns to the tank. In some systems, a conventional boiler may be used to increase the temperature of the water.

Advantages

Solar energy is a renewable energy resource and there are no fuel costs. No harmful polluting gases are produced.

Disadvantages

• solar cells are expensive and inefficient
• solar panels may only produce very hot water in very sunny climates, and in cooler areas may need to be supplemented with a conventional boiler
• does not work at night