Energy And Its Forms

Electricity can be easily converted into any form. Electric current is the means by which electrical energy is most easily transported to places where it is needed and converted into other forms. For e.g: electricity in the heater is converted into heat energy when the bulb glows electricity is converted into light as well as heat energy.

When water is released from the dam, it is in motion. Due to motion, it possesses kinetic energy.

_{As we know,}

k = 1/2(mv²)

mv² = 2k

v² = 2k/m

When water is stored in the tank, it possesses potential energy. Then the water is released and it possesses kinetic energy due to the motion. As the water is in motion it possesses kinetic energy as well as possesses potential energy due to height. so, kinetic energy changes into mechanical energy. This mechanical energy is then stored in a generator using a turbine in the form of electrical energy.

As we know,

potential energy(u) = mgh

(a) u = 980J

(b) u = 988J

(c) u = 7840J

(d) u = 1176J

So, the object with mass 8kg possesses maximum potential energy.

1. watt

The work done by the bulb is measured in joules and time in seconds. So, the unit of power is joules/second, which is equal to watt. So, the unit of power is watt.

2. joule

According to the definition of energy, it is the capacity to do work and work is measured in joules. So the unit of energy is joules.

3. heat and light energy

When a candle burns we can feel the heat around it and can see the light it gives out. So the chemical energy in the candle is transformed in the light as well as heat energy.

4. potential energy

The tank is placed at the height. Due to height, work is done by gravity to pull it downwards. So, the overhead tank possesses potential energy.

5. light and sound energy.

In a cinema theatre what we see is due to electrical energy transformed into light energy and due to sound energy, we can hear the dialogues.

Compressed spring: potential energy

Stretched bow: potential energy

Moving arrow: kinetic energy

Water stored in a dam: potential energy

A stone at the top of a building: kinetic energy

A bird resting on the branch of a tree: potential energy.

Kinetic energy of any object depends upon two factors (a) mass (b) speed

Now as the bus and the car are moving at the same speed, so the kinetic energy of the vehicle having greater mass will be greater. And we know that the mass of the bus is always greater than the mass of the car so the kinetic energy of the bus is greater than the kinetic energy of the car.

Given: Height = 5m.

Mass = 200g = 0.2 kg

g = 9.8ms^-2

Formula used: Potential energy = mgh

⇒ Potential Energy = 0.2 kg × 5m × 9.8 ms^-2

= 9.8 J

When the ball is present at the 5m height it possesses potential energy, which is equal to kinetic energy possessed by the ball when it just reaches the ground.

∴ K.E energy will be = 9.8 J

1. A light bulb and LED are used to convert electrical energy into light energy.

2. A motor is used to convert electrical energy in mechanical energy. For e.g. motor in a fan and pump.

3. Electric iron and electric strove are used to convert electric energy in potential energy.

4. Microphone converts sound energy into electrical energy

5. A battery is a device that stores electrical energy in the form of chemical energy and converts that energy into electricity.

In a mechanical clock potential energy changes into kinetic energy. When the spring is revolved it stores potential energy and when it is released it changes into kinetic energy.

In a quartz clock, electrical energy changes into magnetic energy and then into kinetic energy.

In thermal power station heat energy is converted into electrical energy. The thermal power station, where coals are burnt and the steam produced from it is used to run turbines. This energy is stored as electrical energy in generators.