INVENTION AND INVENTOR

Invention	Inventor	Year	Patent No.
Alternating Current Calculations	Charles Proteus Steinmetz	1897
Alternator	Nikola Tesla	1891	US447,921
Battery (Voltaic Pile)	Alessandro Volta	1800
Cell Phone	Martin Cooper	1973	US3,906,166
Microphone	Emile Berliner	1877	US224,573

BASIC QUESTIONS FOR EEE

                               TODAY QUESTION  FOR CHALLENGERS:

1) Resistivity of a wire depends on
A. material

B. length

C. cross section area

D. all of above

ANS:Resistivity is a basic property of any materials. It is defined as the resistance offered by a cube of unit volume of the materials. Hence resistivity of a wire depends on its material.

2) Resistance of a wire is r ohms. The wire is stretched to double its length, then its resistance will be

A. r/2 

B. 4r

C. 2r 

D. r/4

ANS:Resistance r = ρl/a. When the wire of length l is stretched to 2l, then the cross – sectional area of the wire becomes a/2. Now new value of resistance, r’ = ρ2l/(a/2) = 4ρl/a = 4r.

3) Kirchhoff’s second law is based on law of conservation of

A. charge

B. energy

C. momentum

D. mass

ANS:Kirchhoff’s voltage law (KVL) is also called Kirchhoff’s second law. The principle of conservation of energy implies that the directed sum of the electrical potential differences (voltage) around any closed network is zero. 

4) A circuit contains two un equal resistor in parallel

A. voltage drops across both are same

B. currents in both are same

C. heat losses in both are same

D. voltage drops are according to their resistive value

ANS:Whatever may be the value of resistance the voltage drops, across all the resistors connected in parallel, are always same