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Solution of Work and Energy (Page No - 162) - Physics by Lakhmir Singh, Class 9 | Extra Documents & Tests for Class 9 PDF Download

Page 162
Solution 1
The commercial unit of energy is kilowatt-hour.
Solution 2
One kilowatt-hour is the amount of electrical energy consumed when an electrical appliance having power of 1 kilowatt is used for 1 hour.
Solution 3
Megawatt and kilowatt are the units of power bigger than watt.
Solution 4
1 watt is the power of an appliance which does work at the rate of 1 joule per second.
Solution 5
1 horse power = 746 watt
Solution 6
Power has watt as its physical unit
Solution 7
1 watt
Solution 8
Work done = 1200 J
Time taken = 2 minutes = 2 x 60 = 120 s 

Solution of Work and Energy (Page No - 162) - Physics by Lakhmir Singh, Class 9 | Extra Documents & Tests for Class 9

Solution 9
One kilowatt = 3.6 x 106 J
Solution 10
a) Power
b) Electrical Energy
Solution 11
1 kW-h of electrical energy is commonly known as unit of electricity.
Solution 12
A cell converts chemical energy into electrical energy.
Solution 13
Electric motor
Solution 14
a) Electric generator
b) Cell
c) Electric iron
d) Solar cell
e) Electric bulb
Solution 15
a) Speaker
b) Steam engine
c) Car engine
d) Gas stove
e) Solar water heater
Solution 16
a) Work
b) Joule ; second
c) kWh
d) conservation; transformed; created; destroyed
e) kinetic; potential 

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FAQs on Solution of Work and Energy (Page No - 162) - Physics by Lakhmir Singh, Class 9 - Extra Documents & Tests for Class 9

1. What is work and energy in physics?
Ans. In physics, work is defined as the transfer of energy that occurs when a force is applied to move an object over a certain distance. Energy, on the other hand, is the ability to do work. Both work and energy are closely related concepts in physics.
2. How is work calculated?
Ans. Work is calculated by multiplying the force applied to an object by the distance over which the object is moved in the direction of the applied force. The formula for calculating work is: Work = Force × Distance × Cosine of Angle between Force and Displacement.
3. What are the different forms of energy?
Ans. There are several different forms of energy, including kinetic energy (energy of motion), potential energy (stored energy), thermal energy (heat energy), chemical energy (energy stored in chemical bonds), electrical energy (energy of electric charges), and nuclear energy (energy stored in the nucleus of an atom), among others.
4. How is energy converted from one form to another?
Ans. Energy can be converted from one form to another through various processes. For example, in a car engine, chemical energy from fuel is converted into thermal energy, which is then converted into mechanical energy to move the car. This conversion of energy from one form to another is governed by the principle of conservation of energy.
5. What is the unit of work and energy?
Ans. The unit of work and energy is the joule (J) in the International System of Units (SI). However, other common units of energy include the calorie (cal) and the kilowatt-hour (kWh).
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