Questions with Answers

Energy ( Term 1 Chapter 3 | 5th Science)

Evaluation

I. Choose the correct answer.

1. When diesel is burnt chemical energy is converted into ________

a) wind energy

b) heat energy

c) solar energy

d) sound energy

Answer: b) heat energy

2. Running water possesses ______

a) potential energy

b) chemical energy

c) kinetic energy

d) sound energy

Answer: c) kinetic energy

3. Unit of energy is ________

a) kilo gram

b) newton

c) kelvin

d) joule

Answer: d) joule

4. Which one of the following requires wind energy?

a) Bicycle

b) Photosynthesis

c) Parachute

d) Automobiles

Answer: c) Parachute

5. Cow dung possesses ______

a) kinetic energy

b) chemical energy

c) solar energy

d) heat energy

Answer: d) heat energy

II. Find out the energy conversion that takes place in the following.

1. Iron box : Chemical energy → Heat energy

2. Electric Iron box : Electrical energy → Heat energy

3. Electric fan : Electrical energy → Mechanical energy

4. Speaker : Electrical energy → Sound energy

5. Generator : Heat energy → Electrical energy

III. Find out the form of energy possessed by the following things.

1. A rock on the top of a hill – Potential energy

2. A rolling ball – Kinetic energy

3. Charcoal – Potential energy

4. Water falls - Kinetic energy

5. Battery – Electrical energy

IV. Match the following.

Electric bell - Solar energy

Water in dam - Light energy

Solar heater - Electrical energy

Wind mill - Potential energy

Torch light - Sound energy

Answer:

1. Electric bell - Sound energy

2. Water in dam - Potential energy

3. Solar heater - Solar energy

4. Windmill - Electrical energy

5. Torchlight - Light energy

V. Say True or False.

1. An apple falling from a tree is an example for kinetic energy. (True)

2. Electrical energy is used to run electric trains. (True)

3. Heat energy cannot be produced by friction. (False)

(Heat energy can be produced by friction)

4. Potential energy and heat energy are the two forms of mechanical energy. (False)

(Potential energy and kinetic energy are the two forms of mechanical energy )

5. The unit of energy is joule. (True)

VI. Answer in brief.

1. What is energy?

In science, energy is defined as capacity to do work.

2. What are the different forms of energy?

There are different forms of energy like mechanical energy, heat energy, light energy, wind energy etc.

3. What are the uses of mechanical energy.

Uses of mechanical energy

Mechanical energy can be used to do many works. Some of them are given below.

• In hydro electric plants, kinetic energy of water is converted into electrical energy.

• Windmills convert kinetic energy of winds into electrical energy.

• Mechanical energy of the hammer is used to apply a force on a nail.

• Mechanical energy can bring a moving body to rest and make a body at rest to move.

4. State the law of conservation of energy.

Law of conservation of energy states that energy can neither be created nor be destroyed. One form of energy is converted into another form of energy. This law was given by Julius Robert Mayar.

5. Mention the uses of light energy.

Uses of light energy

• We are able to see objects with the help of light energy.

• Plants use light energy to synthesise their food.

• With the help of light energy, our skin is able to synthesise Vitamin-D.

• Electricity can be produced with the help of light energy.

VII. Answer in detail.

1. Explain the types of mechanical energy.

Energy possessed by an object due to its position is called mechanical energy.

Mechanical energy can be classified into two.

• Kinetic energy

• Potential energy

Kinetic energy : Energy possessed by a moving object is known as kinetic energy. It is also known as energy of motion.

Examples: Moving car, Cricket ball bowled by a player, Bullet coming out of a gun.

Potential energy : Energy possessed by an object which is at rest is known as potential energy. It is also known as stored energy of position.

Examples: Stone in the stretched rubber. Water in the dam.

Mechanical energy can be used to do many works. Some of them are given below.

• In hydro electric plants, kinetic energy of water is converted into electrical energy.

• Wind mills convert kinetic energy of winds into electrical energy.

• Mechanical energy of the hammer is used to apply a force on a nail.

• Mechanical energy can bring a moving body to rest and make a body at rest to move.

2. Explain conservation of energy.

Conservation energy

Energy cannot be created and it cannot be destroyed also. It is changed from one form to another form or transferred from one object to another object. We can say many examples for conservation of energy in our daily life.

1. Water Dam

Water stored in water dams possesses potential energy. When water falls down, potential energy of water is converted into kinetic energy. Kinetic energy of water rotates the turbines and electric energy is generated.

2. Electrical Appliances

Electric energy is used in many domestic appliances such as electric stove, iron box and fan. Electric energy flows into the coil in the devices. As current flows, it heats up the coil. With the help of this heat energy, we do many useful works. Thus, electrical energy is converted into heat energy. Electical energy is converted to mechanical energy in fan, light enrgy in bulb and sound energy in computer.

3. Driving a Car

We use fuel in the form of petrol or diesel or gas to run vehicles. When this fuel burns in the engine, chemical energy is converted into heat energy. Burning fuel produces hot gases which pushes the piston in the engine to move the vehicle. Thus heat energy is converted into mechanical energy.