Ans: The rate of doing work is called power. Its unit is joule/second.
P=w/t(Power=Work/time).
2Q: What is electrical power?
Ans: The rate of doing work by an electrical machine is called its power.
It is expressed in watts. 1 watt = 1 joule/second.
3Q: What is horse power?
Ans: Horse power is the commercial unit of mechanical power, where, 1 H.P = 746 watts.
4Q: What is M.H.P.?
Ans: M.H.P.(metric horse power) is the internationally agreed unit of mechanical power.
1 M.H.P. = 735 watts.
5Q: What are the main types of mechanical energy?
Ans: There are two main types of mechanical energy - (1) Kinetic energy and (2) Potential energy.
6Q: What is meant by kinetic energy?
Ans: A moving object is said to possess kinetic energy.
K.E. = 1/2 m.V^2(1/2 X mass X velocity^2).
7Q: What is meant by potential energy?
Ans: An object raised above the earth's surface is said to possess potential energy.
P.E. = m.g.h.(mass X g X height).
8Q: What are the principal effects of electric current?
Ans: The principal effects of electric current are - (1) Magnetic (2) Heating and (3) Chemical effect.
9Q: What is heating effect of current?
Ans: A current carrying conductor becomes hot.
H = I^2.R.t(current^2 X resistance X time).
10Q: What is magnetic effect of current?
Ans: A current carrying conductor is surrounded by a magnetic field.
11Q: What is chemical effect of current?
Ans: A flow of electric current through an inorganic solution decomposes the same into ions.
m = Z.I.t(E.C.E. X current X time).
12Q: What is Ohm's Law?
Ans: In a closed d.c. circuit the p.d. (V) developed across a conductor is directly proportional to the current (I) flowing through it if the temperature and other physical conditions of the conductor have been kept constant. V is directly proportional to the I. or V/I = constant or V/I = R.
Where, R = Resistance of the conductor.
13Q: What is resistance law?
Ans: The resistance (R) of a conductor is directly proportional to length (l) and inversely proportional to cross-sectional area (A) of the conductor.
14Q: What is meant by resistivity?
Ans: The resistance of a piece of a material having a length of one cm and a cross-sectional area of one square cm is called its resistivity or 'specific resistance'. p(ro) = (R X A)/l.
15Q: What is meant by temperature co-efficient?
Ans: The change in resistance of a resistor by increasing its temperature by 1 degree Celsius is called the temperature coefficient of the resistor's material.
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