Types of Energy

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  • April 12, 2023
9th Physics Ch#08 Energy Sources And Transfer Of Energy Types of Energy

Energy

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“The ability to do work is called Energy”

Unit:

The S.I unit of energy is joule (J).

Kinetic Energy:

“Energy possessed by an object due to its motion is called kinetic energy.”

Unit:

The S.I unit of energy is joule (J).

Kinetic energy depends upon:

The mass m of the object- the greater the mass, the greater its K.E 

The speed v of the object- the greater the speed, the greater the K.E

Derivation of the Equation, K.E = ½ mv2:

To obtain an expression for K.E we have to determine the work done by the body in motion. This work is equal to the kinetic energy of the body.
Consider a body of mass ‘m’ placed on a horizontal surface initially at rest. When a force ‘F’ is applied it covers a distance ‘S’ and its final velocity becomes ‘v’. Then work done is:

W = F . S …… (i)

But by the second law of motion when a force acts on a body it produces acceleration in the direction of the force.

F = ma

And by using the third equation of motion i.e.:

vf2 – vi2 = 2aS
When
vi = 0,
vf = V and
S = ?
therefore,
v2 – 0 = 2aS

Example:

  1. Sailing boat.
  2. Moving air.
  3. Driving a car.

Potential Energy:

“The energy that body possesses by virtue of its position, shape or state of a system.”

  It is also defined as:

“The work done stored in a body in lifting it to a height “h”.

Mathematically it can be written as

  𝑷. 𝑬 = 𝒎𝒈𝒉

Unit:

The S.I unit of energy is joule (J).

There are different types of potential energy. Like gravitational potential energy, elastic

 potential energy, and chemical potential energy.

  1. A body raised to a height “h” above the ground has gravitational potential energy.
  2. A stretched spring has elastic potential energy due to its stretched position (condition).
  3. The energy stored in the plants that we eat is chemical potential energy

                                                              

Derivation of Potential Energy:

To derive the expression for gravitational potential energy, let us consider an object of mass “m” which is raised up through height “h” from the ground. The work done in lifting it to height “h” is stored in it as its gravitational potential energy “P∙E”, i.e.

P∙E = Work done
P∙E = W

We know that W = F.d, therefore

P∙E = F ∙ d

We also know that F = mg (weight), therefore

P.E = (mg) . d

Here d = h (height), therefore

P∙E = (mg) ∙ h

Hence, equation becomes:

P∙E = mgh ……….. (i)
chp 8 phy ix fig 6

Conversion of Energy:

Energy neither be created nor it can be destroyed but it can be converted from one form to another form. This is called the law of conservation of energy.

Conversion of Energy From One Form To Another Form:

Fossil Fuel Energy:
  1. Fossil fuel energy is produced from ancient plants and animals that have undergone a  transformation into crude oil, coal, natural gas, or heavy oils due to heat and pressure  in the Earth’s crust over many millions of years. These fossil fuels store a significant   amount of chemical energy.
  2. This stored energy is then converted into heat and light energy through oxidation, also known as burning. When a fossil fuel such as charcoal is burned, it releases heat and light energy.
     Hydroelectric Energy:
    1. Hydroelectricity is a type of electricity that is generated through the use of hydropower. This involves harnessing the gravitational force of flowing or falling water to generate power
    2. One of the most widely used methods of producing hydroelectricity is through the use of a dam on a river. This involves storing water in a reservoir and then releasing it to flow through a turbine, which spins and drives a generator to produce electricity.
            
      Solar Energy:
      1. Solar energy refers to the energy that is radiated from the sun and is abundant in Pakistan.
      2. There are various devices that can harness this solar energy and convert it into either electrical energy or heat energy. Examples include photovoltaic solar panels and solar cells, which convert the sun’s rays into electricity for various purposes.
      3. Solar heaters are also used to convert solar energy into heat energy, which can be used to heat water tanks and indoor spaces.
              
      Geothermal Energy:
      1. Geothermal energy is stored in the Earth as natural heat, which originates from the hot molten part called magma deep in the Earth. When water is in close proximity to the magma, it becomes steam due to the high temperature and this thermal energy is conducted to the Earth’s surface. 
      2. A geothermal power plant harnesses this energy to generate electricity through the use of an electrical generator. Geothermal wells can be created by drilling deep near hot rocks at various locations where magma is close to the surface. The hot rocks heat the water that is pumped into the well, causing it to change into steam. This steam can be used either for heating or to power an electrical generator.

      Wind Energy:

      1. The energy obtained by the wind is called wind energy. It is generated by windmills. A windmill consists of a turbine that rotates due to wind. Kinetic energy is produced due to the motion of the turbine.
      2. Wind turbines convert this kinetic energy into mechanical power. A generator converts that mechanical power into electricity.
      3. Applications:
      • It is being used as the source of energy for sailing ships in oceans.
      • It is being used by windmills to pump water. It is being used by windmills to grind grain. 
      • It is used to turn wind turbines to produce electricity.

       Biomass Energy:

      1. Biomass is the organic material that comes from plants and animals. Biomass consists of stored energy from the Sun, garbage, wastes, sugarcane, etc. Solid biomass, such as wood, organic material, and garbage, can be burned directly to produce heat.
      2. Biomass can also convert into a gas called biogas and into liquid biofuels such as ethanol and biodiesel.
      Tidal Energy:
      1. It is a form of hydropower that converts the energy obtained from tides into a useful form of power mainly electricity as the Earth uses the gravitational forces of both the moon and the sun every day to move vast quantities of water around the oceans and seas producing tides and in this way energy is produced called tidal energy.
      Renewable Energy Source Non-Renewable Energy Source
      Renewable resources are replenished naturally and at a rate that is equal to or faster than their rate of consumption. Non-renewable resources are finite and once they are used, they cannot be replenished.
      Renewable energy sources are clean and produce little to no pollution. Non-renewable energy sources are often associated with pollution and negative environmental impact.
      Renewable energy sources, such as wind, solar, and hydropower, are widely available and can be generated in many parts of the world. Non-renewable energy sources, such as coal, oil, and natural gas, are often limited to specific geographic locations and can be subject to supply disruptions.

      Quiz

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