1. If a coil of 150 turns is linked with a flux of 0.01wb when carrying a current of 10 Amps. If this current is uniformly reversed in 0.01 second, then the induced emf in the coil is
Answer : 300 V
Explanation:-
Given N=150, ∅=0.01wb, t=0.01sec, I=10Amps
L=(N∅)/I=(150*0.01)/10=0.15H
e=L*di/dt=0.15*[10-(-10)]/0.01
e=0.15*2000
e=300 V
2. According to Coulomb's law the force exerted between two point charges is
Answer : Inversely proportional to the square of the distance between the charges
Explanation:-
3. An ammeter reads up to 1 A. The meter resistance is 0.81 ohm. To increase the range of themeter to 10 A, the value of the required shunt is
Answer : 0.09 Ω
Explanation:- Given Im=1A, Rm=0.81 Ω, I=10A
Rsh=Rm/(m-1)
m=I/Im=10/1==10
Rsh=Rm/(m-1)==0.81/(10-1)
Rsh=0.81/9=(81/100)*9
Rsh=9/100
Rsh=0.09 Ω
4. A 230 V single phase Energy Meter has a constant load of 4 A passing through it for 6 hours at unity power factor. If the meter disc makes 2208 revolutions during this period, then the meter constant is
Answer : 400 rev/kwh
Explanation:- Given V=230V, I=4 A,h=6hrs,cos∅=1
Kwh=(230*4*1*6)/1000
Kwh=5.52
Given the meter disc makes 2208 revolutions for 5.52Kwh units
Meter constant=Number of revolutions /Kwh
Meter constant=2208/5.52
Meter constant=400 rev/kwh
5. PMMC type instrument normally use
Answer : Eddy current damping
Explanation:-
6. Which of the following instruments can be used only for AC measurements
Answer : Moving iron
Explanation:-
7. Aluminium is used for making pointers of measuring instruments because it is
Answer : lighter in weight
Explanation:-
8.Thermocouples are
Answer : Active transducers
Explanation:-
9. If the field winding of a running d.c shunt motor suddenly opens then
Answer : its speed becomes dangerously high
Explanation:-
10. The speed of a DC Shunt motor can be increased above its normal speed by
Answer : decreasing the field current
Explanation:- Speed is inversly proportional to the flux
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