Board | RBSE |
Class | Class 8 |
Subject | Science |
Chapter | Chapter 9 |
Chapter Name | Work and Energy |
Number of Questions Solved | 33 |
Category | RBSE Solutions |
I. Multiple Choice Questions
Question 1.
Answers:
Question 2.
Pill in the blanks.
Answers;
Question 3.
Match the column A with column B.
(A) Energy conversation | (B) Instruments |
(i) Electrical energy to sound energy | (a) Solar cell |
(ii) Electrical energy to heat energy | (b) Dynamo (generators) |
(iii) Mechanical energy to electrical energy | (c) Electric heater |
(iv) Light energy to electrical energy | (d) Speaker |
Answer:
(A) Energy conversation | (B) Instruments |
(i) Electrical energy to sound energy | (a) Speaker |
(ii) Electrical energy to heat energy | (b) Electric heater |
(iii) Mechanical energy to electrical energy | (c) Dynamo (generators) |
(iv) Light energy to electrical energy | (d) Solar cell |
Question 1.
Define work.
Answer:
The action for producing the displacement by exerting force on object is called work.
Question 2.
What are the things on which work done on the object depend?
Answer:
(i) Distance covered by an object.
(ii) Amount of force applied on it, thus, Work = Force x Displacement.
Question 3.
Give the two names which store kinetic energy and potential energy in it on the basis of daily life observation.
Answer:
Water in the overhead tanks and striking hammer have potential as well as kinetic energies. Flying bird and running fan have both potential as well as kinetic energies.
Question 4.
How do we define heat energy conversation? Explain energy transfer on the basis of three different examples.
Answer:
Energy stored in burinng objects of hot objects. When this energy is converted from one form into another form, it is called heat energy conversation.
Examples:
(a) Electric heater converts electric energy to heat energy.
(b) Solar cell converts light energy to electric energy.
(c) Electric generator converts mechanical energy to electric energy.
Question 1.
What do you mean by global energy crisis? What are the measures adopt to resolve the global energy cirisis? Describe it in detail.
Answer:
Due to growing population and development in different fields, demand and use of traditional energy sources is continuously increasing. The storage of deposits of these resources is limited, a day will come when these deposits would exhaust if their use is done with the same speed and manner. It would result into energy crisis. Hence it is essential that we should use them wisely and try to find alternate sources of energy and increase their use.
Measures of conservation energy:
Question 2.
Explain the differences between conventional energy sources and non-conventional energy sources with providing suitable example.
Answer:
The differences between conventional energy sources and non-conventional energy sources are as follows:
Conventional sources of energy | Non-conventional sources of energy |
(i) Their decomposition rate is less than the consumption rate. | (i) Their decomposition rate is higher than the consumption rate. |
(ii) These sources of energy can be used limited and in controlled quantity as their reserves are limited. | (ii) These sources of energy can be used continuously because their reserves are unlimited. |
(iii) Traditional sources of energy create pollution. | (iii) Non-traditional sources of energy are environment friendly hence do not create pollution. |
(iv) These are limited energy sources. | (iv) These are unlimited energy sources. |
(v) Petrol, diesel, coal, natural gas, etc. fossil fuels and wood are traditional sources of energy used by us. | (v) Sun, sea, water, air’ and earth, etc. are non-traditional sources of energy. |
I. Multiple Choice Questions
Question 1 .
When the displacement produced in a body is perpendicular to the direction of applied force then work done is:
(a) 1 Joule
(b) Zero Joule
(c) 103 Joule
(d) None of these
Question 2.
Energy possesse by virtue of its position is called-
(a) Mechanical energy
(b) Chemical energy
(c) Kinetic energy
(d) Potential energy
Question 3.
Which of the following is not a fossil fuel?
(a) Fire wood
(b) Natural gas
(c) Wind energy
(d) Kerosene
Question 4.
Which of the following converts chemical energy into electrical energy?
(a) Solar cell
(b) Bulb
(c) Battery
(d) Dynamo
Question 5.
When the velocity of a body is doubled, then its kinetic energy will become
(a) 8 times
(b) 4 times
(c) 16 times
(d) None of these
Question 6.
What type of energy is used to run submarine?
(a) Wind energy
(b) Ocean energy
(c) Atomic”energy
(d) None of these
Question 7.
Energy obtained from the Sun, wind, water, bio waste, oceans, underground energy is known as
(a) Non- conventional energy
(b) Conventional energy
(c) Ocean energy
(d) None of these
Question 8.
The energy of tides and currents in ocean can be converted into electrical energy, such energy is known as:
(a) Mechanical energy
(b) Ocean energy
(c) Atomic energy
(d) None of these
Question 9.
The unit of energy is
(a) Watt
(b) Kilometre/hour
(c) Joule/sec
(d) Watt/sec
Question 10 .
The combination of kinetic energy and potential energy is
(a) Electrical energy
(b) Mechanical energy
(c) Geo-thermal energy
(d) Bio energy
Question 11 .
Which form of energy is contained in wind energy?
(a) Kinetic energy
(b) Potential energy
(c) Electric energy
(d) Thermal energy
Answers:
1. (b)
2. (d)
3. (c)
4. (c)
5. (b)
6. (c)
7. (a)
8.(b)
9. (a)
10. (b)
11. (c)
Question 1.
Define the term energy. Give its S.I unit.
Answer:
The capacity of doing work is called energy. Its S.I unit is Joule.
Question 2.
Name the place, where the atomic power plant is located in Rajasthan.
Answer:
Rawatbhata in Chittorgarh, Rajasthan.
Question 3.
What is the full form of LPG?
Answer:
The full form of LPG is Liquified Petroleum Gas.
Question 4.
Define Geo-thermal energy?
Answer:
Energy persent in the depth of the earth is called Geothermal energy. As we move inside the earth from the earth surface the temperature increases with increasing depth. This heat energy can be converted into electrical energy.
Question 5.
Define wind mill. Give its two uses.
Answer:
Wind mill is a machine which convert wind energy into mechanical energy. Wind mills are used for grinding of wheat and lifting water from the well.
Question 6.
What are renewable energy sources?
Answer:
Non conventional energy sources are called renewable energy sources. These are the sources which can be re-constituted or redeveloped. Important non conventional energy sources are solar energy, wind energy, bio mass, bio gas etc.
Question 7.
What is the other name of conventional energy sources?
Answer:
Conventional energy sources are also known as non renewable energy sources. Those energy sources which cannot be re-plenished such as coal, petrol, water, nuclear power etc. are non-renewable sources.
Question 8.
Define fossil fuel.
Answer:
Millions of years back when plants vegetation and animals present at that movement were supressed in the earth due to the excessive pressure and temperature is known as fossil fuel. Example are coal, petroleum, gas etc.
Question 9.
Write at least five form of energy.
Answer:
Mechanical energy i.e. (K.E + P.E), heat energy, chemical energy, atomic energy, wind energy.
Question 10.
What do you mean by potential energy? Explain with example.
Answer:
The energy which a body possess due to its position or due to change in the shape is called potential energy.
Example 1: A brick which is suspended above the ground has energy because it would do work by falling to the ground. Its energy is due to its position and therefore it is potential energy.
Example 2: The potential energy of a stretched bow string results from a change in its shape.
Question 1.
What is bio-mass energy? What are its uses?
Answer:
The excreta of animals, cow dug, wild plants and dry leaves of plants are fermented in a digestive tank. The produced gas is called bio gas/Gobar gas which is known as bio mass energy. This gas bums with smokless flame. Therefore it is a non polluting gas. This is used as a house fuel and for lighting the house. ‘
Question 2.
Define the following terms:
Answer:
Question 3.
Answer:
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