ECET EEE 2009-3

1. Four equal charges of Q coulombs are placed across the corners of a square of radius a. the electric field intensity at the centre of the square will be

A. Q/4π^(εοa)
B. Q/2π^(εοa)
C. Q/π^(εοa)
D. none

Answer : Q/π^(εοa)
Explain:-

2. The resistance of incandescent lamp of 100W, 100V is

A. 100 Ω
B. 1000 Ω
C. 10 Ω
D. 2000 Ω

Answer : 100 Ω
Explain:- V=100v, P=100w
According to ohms law V=IR, I=V/R
P=VI=V^2/R
R=V^2/P= (100^2)/100=100 Ω

3. Polarisation in Voltaic cell results in

A. Oxygen at cathode
B. Hydrogen at cathode
C. Hydrogen at anode
D. Oxygen at anode

Answer : Oxygen at anode
Explain:-

4. Magnetic field intensity due to a very long conductor carrying a current of 1 amps, at a distance d' from the conductor in A/m is

A. 1/2πd
B. 1/4πd
C. 1/8πd
D. 1/πd

Answer : 1/2πd
Explain:-

5. The maximum magnetic force on a conductor carrying a current of 1 amp when placed at right angles at the magnetic field of B wb/m2 and of length 'L' in Newton is

A. BIL
B. BIL sin θ
C. 2 BIL
D. BIL/2

Answer : BIL
Explain:-

6. The probable leakage coefficient for electrical machines is

A. 1
B. 12
C. 3
D. 4

Answer : 1
Explain:-

7. The following is a donar material

A. gallium
B. antimony
C. Boron
D. Iridium

Answer : antimony
Explain:-

8. Silicon controlled rectifier (SCR) acts as

A. A bidirectional switch
B. An amplifier
C. An unidirectional switch
D. An oscillator

Answer : An unidirectional switch
Explain:-

9. In doping of semiconductors, the following is added

A. impurity like antimony
B. chemical
C. water
D. copper

Answer : impurity like antimony
Explain:-

10. A D.C generator works on the principle of

A. Fleming's left hand rule
B. Fleming's Right hand rule
C. Lenz's law
D. Faraday's laws of electromagnetic induction

Answer : Faraday's laws of electromagnetic induction
Explain:-