# Various Forms Of Energy Class-8th Goyal Brothers ICSE Physics Solution Chapter-4 Unit-3

Various Forms Of Energy Class-8th Goyal Brothers ICSE Physics Solution Chapter-4 Unit-3. We Provide Step by Step Answers of Objective, True False, Incorrect and Correct, Fill in the blanks, Match the following , Short/Long Answer Type of Chapter-4 (Energy), unit-3 (Various Forms Of Energy) Visit official Website  CISCE  for detail information about ICSE Board Class-8.

## Various Forms Of Energy Class-8th Goyal Brothers ICSE Physics Solution Chapter-4 Unit-3

 Board ICSE Class 8th Subject Physics Book Name Goyal Brothers Chapter-4 Energy Unit-3 Various Forms Of Energy Topic Solution of exercise questions Session 2023-24

### OBJECTIVE QUESTION

Various Forms Of Energy ICSE Class-8th Goyal Brothers Physics Solution Chapter-4 Unit-3

#### Que: A. Fill in the blanks spaces by choosing the correct words from the list given below :

List : chemical, light, heat, electric, kinetic

1. In hydroelectric dams the kinetic energy of flowing water is transformed into electric energy.

2. Nuclear energy is released in the form of heat energy when an atom splits.

3. During photosynthesis, the light energy changes into chemical energy.

4. During digestion of food the chemical energy of food changes into heat energy.

5. A loudspeaker converts electric energy into sound energy.

#### Que: B. Write ‘True’ or ‘False’ for the following statements :

 Statement True/False 1. Magnetic energy always causes attraction. F 2. The energy in an electric cell is stored in the form of chemical energy. T 3. An electric bulb converts electric energy into heat energy only. F 4. The source of energy in a nuclear bomb is its chemical energy. F 5. In electric wind stations, the potential energy of wind changes into electric energy. F

#### Que: C. Statements given below are incorrect. Write the correct statements :

##### Question: 1. During the charging of a car battery, the chemical energy changes into electric energy.

Answer: During the charging of a car battery, the electric energy changes into chemical energy.

##### Question: 2. During photosynthesis by plants the heat energy changes to chemical energy.

Answer: During photosynthesis by plants the light energy changes to chemical energy.

##### Question: 3. When we speak in front of a microphone, the electric energy changes into sound energy.

Answer: When we speak in front of a microphone, the sound energy changes into electric energy.

##### Question: 4. When an electric current flows through an electric bulb, the electric energy first changes to light energy and then to heat energy.

Answer: When an electric current flows through an electric bulb, the electric energy first changes to heat energy and then to light energy.

##### Question: 5. The energy released during disintegration of nucleus of an atom is in the form of light energy.

Answer: The energy released during disintegration of nucleus of an atom is in the form of sound energy.

#### Que: D. Tick (√) the most appropriate answer :

##### 1. Burning of paper is an example of conversion of :

(a) heat energy into light energy

(b) chemical energy into heat energy

(c) chemical energy into light energy

(d) both (b) and (c)

Answer: option (d) both (b) and (c) is correct.

##### 2. The ultimate source of energy on the planet earth is :

(a) sun

(b) coal

(c) petroleum products

(d) molten lava within the earth

Answer: option (a) sun is correct.

##### 3. The cause of water cycle in nature is :

(a) chemical energy

(b) nuclear energy

(c) solar energy

(d) kinetic energy of wind

Answer: option (c) solar energy is correct.

##### 4. Strong wind turns the blades of wind turbine because it possesses :

(a) potential energy

(b) kinetic energy

(c) both (a) and (b)

(d) none of these

Answer: option (b) kinetic energy is correct.

##### 5. When a person speaks in front of a microphone, the sound energy changes into :

(a) loud sound energy

(b) magnetic energy

(c) chemical energy

(d) electric energy

Answer: option (d) electric energy is correct.

#### Que: E. Match the statements in Column A, with those in Column B :

 Column A Column B 1. A device which converts electric energy into heat energy only. (a) Microphone 2. A device which converts electric energy into mechanical energy. (b) Electric generator 3. A device which converts sound energy into electric energy. (c) Electric motor 4. A device which converts light energy into electric energy. (d) Electric geyser 5. A device which converts mechanical energy into electric energy. (e) Photo-voltaic cell

Answer:

 Column A Column B 1. A device which converts electric energy into heat energy only. (a) Electric geyser 2. A device which converts electric energy into mechanical energy. (b) Electric motor 3. A device which converts sound energy into electric energy. (c) Microphone 4. A device which converts light energy into electric energy. (d) Photo-voltaic cell 5. A device which converts mechanical energy into electric energy. (e) Electric generator

### STUDY QUESTION

Various Forms Of Energy ICSE Class-8th Goyal Brothers Physics Solution Chapter-4 Unit-3

#### Question: 1. (a) What is mechanical energy?

Answer: Mechanical energy is the sum of kinetic energy and potential energy. It describes the energy of a body because of its motion or position or both.

#### (b) What kind of energy changes take place in the bodies of living beings, so as to produce mechanical energy.

Answer: When you eat food, your body can use the chemical energy in the food to make your muscles move so you can breathe, walk, run, jump, lift things, and do all the other things you need to do to live. The chemical energy in the food gets changed into the mechanical energy of moving muscles.

#### Question: 2. (a) Give a simple example to prove that heat is a form of mechanical energy.

Answer: The water in the pressure cooker is converted into steam by the heat energy in the burning flame under the pressure cooker. The water and the steam get energy from the heat. This energy works by displacing the nozzle.

#### (b) Name three devices/industries in which heat energy is put to some useful work.

Answer: The internal combustion engine used in cars, or the steam engine (Heat → Mechanical energy) Ocean thermal power (Heat → Electrical energy) Hydroelectric dams (Gravitational potential energy → Electrical energy) Electric generator (Kinetic energy or Mechanical work → Electrical energy.

#### Question: 3. (a) Give example to prove (i) light energy changes into chemical energy (ii) light energy changes into electric energy.

Answer: (i) In photosynthesis chlorophyll transforms light energy to chemical energy.

(ii) solar panels take sunlight from sun in day time and convert it into electric energy.

#### Question: 4. (a) Give a simple example to prove that sound is kind of energy.

Answer: when a person hits the drum with a stick, the kinetic energy of the stick is transferred to the drum and the drum produces sound.

#### (b) Name a device which converts sound energy into (a) electric energy (b) magnetic energy.

Answer: (a) Microphones are a type of transducer – a device which converts energy from one form to another. Microphones convert acoustical energy (sound waves) into electrical energy (the audio signal).

(b) The device that converts sound energy into magnetic energy is called a microphone.

#### Question: 5. (a) Why is electric energy considered most desirable forms of energy?

Answer: It can be quickly transferred from one location to another. It can be generated easily. It can be stored in the form of batteries. It can be easily converted into other forms of energy like thermal energy, mechanical energy.

#### (i) heat energy only (ii) heat and light energy (iii) mechanical energy (iv) magnetic energy

Answer: (i) The devices in which electricity is converted into heat Electric heater and electric iron.

(ii)name any two devices which convert electrical energy into heat energy heat and energy in and light energy mechanical energy and magnetic energy. (1) Heater and home appliances like press iron, geyser etc, converts electrical energy into heat energy. (2) Electric bulb and rods converts heat energy to light energy.

(iii) Electric motor are of 2 types which converts electrical energy into mechanical energy. AC motor: Converts alternating current into mechanical power. DC motor: Converts direct current into mechanical power.

(iv) Generator and transformer converts electric energy into magnetic energy.

#### Question: 6. Explain what is chemical energy. To what uses is this energy put?

Answer: Chemical energy is released when a substance undergoes a chemical reaction and produces heat mostly in the form of a by-product. This reaction is known to be an exothermic reaction. Some of the examples of stored chemical energy include natural gas, biomass, coal, petroleum and batteries.

#### Question: 7. Briefly, describe nuclear energy and its (a) one use (b) one misuse.

Answer: (a) one use: nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant.

(b) one misuse: nuclear power could mean terrorists attempting to steal plutonium to make a crude nuclear weapon or to contaminate the environment as an act of blackmail.

#### Question: 8. Give three examples of inter-conversion of chemical energy into other forms of energy.

Answer: (i) Power plants → electrical energy

(ii) Car → kinetic energy

(iii) space shuttle →  mechanical energy

#### Question: 9. By giving examples, explain how sun is the ultimate source of energy on planet earth.

Answer: The sun’s solar energy is used up by plants during the photosynthesis process. As a byproduct of photosynthesis, oxygen is released into the atmosphere. As a result, we can say that the sun provides an indirect source of oxygen to living things.

#### Question: 10. State difference between energy and power.

Answer:

 Energy Power 1. Energy is the capacity of a body to do work. It id the amount of energy produced or consume by a source in one second. 2. The energy produced or consumed does not depend on time. The power produced or consumed depends upon the time. 3. SI unit of energy is joule (J). SI unit of power is watt (W).

— : end of Various Forms Of Energy ICSE Class-8th Goyal Brothers Physics Solution Chapter-4 Unit-3 :–-

Return to- ICSE Class -8 Goyal Brothers Physics Solutions

Thanks

Please share with your friends if you find it useful

This site uses Akismet to reduce spam. Learn how your comment data is processed.