Heat energyLesson three

We get heat through many ways such as-:

1.The sun.2.friction.

Friction:- It is a method to generate heat as a

principle of converting the kinetic energy (mechanical energy) into heat energy.

The production of heat:- Mechanical energy change into

heat energy by friction. Kinetic energy change to heat

energy be friction.

The heat energy-:It is a form of energy which is

transferred from the object of higher temperature to that

of lower one. The temperature:- It is the heat condition which state

the direction of heat energy whether from or to the object when it comes in cannot with another.

Heat transfer by conduction:-

It is the transfer of heat through solids from the part of higher temperature to the part of lower temperature.

By convection:-

It is transfer of heat in gases and liquid ,where hot molecules which have less density rise up words

,while colder molecules which have more density fall down.

By radiation:-

It is the transfer of heat from hot object to another without any need for material medium through which heat transfers.

Give reason:-

The electric heater is placed at the bottom of the room.

When air around the heater is heated , its density decreases so , it rise up to the room , while the colder air falls down to be heated again and so on.

The heat of the sun does not reach to ground by convection or conduction.

it is not transferred by convection ,because there is vacuum between the sun and the air and it is not transferred by conduction because the air is bad conductor of heat.

The technological application:-

Some of these application work by:-

The solar energy(permanent resource of energy).

The petro (non-permanent resource of energy).

the electricity (a renewable resource of energy).

The effect on the environment.

The kind of energy resource.

The resource of energy depending on it.

The device

Non-polluted

renewable electricity Electric heater:Water heater:

Non-polluted

permanent The sun Solar heater:

Non-polluted

renewable electricity Electric stove:

polluted Non-renewable

Petroleum derivation

Gas or petrol stove:

polluted Non-renewable

Natural gas

Gas oven:

polluted Non -renewable

coal Coal fire