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EXAM DATES: 26 SEPT TO 30 SEPT
DFCCIL’21 EE: Daily Practices Quiz 13-Sep-2021
Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 08 min.
Q1. In an induction motor, at speeds near to synchronous speed, the torque-slip characteristics curve is….
(a) Parabola
(b) Hyperbola
(c) Ellipse
(d) Straight line
Q2. For normal biasing, the emitter junction of BJT has:
(a) Low resistance
(b) No resistance
(c) High resistance
(d) Very high resistance
Q3. In a semiconductor, Drift current is due to:
(a) Diffusion of charge
(b) Applied electric field
(c) Volume gradient
(d) Concentration gradient
Q4. Which of the following generator has zero percent regulation?
(a) Flat compound
(b) Over compound
(c) Under compound
(d) Both a and c
Q5. If an ammeter is connected, like a voltmeter, across the load circuit,
(a) The reading will be low
(b) Almost no current will flow through the meter
(c) The loading effect will be low
(d) An inadmissibly high current will flow through the meter and meter may burn out
Q6. Moving iron and PMMC instruments can be distinguished from each other by looking at
(a) Pointer
(b) Terminal size
(c) Scale
(d) Scale range
SOLUTIONS
S1. Ans.(d)
Sol. Torque=(KsR2 E20^2)/(R2^2+(SX20 )^2 )
When the speed is very near to synchronous speed, the slip is very low, and (sX_20 )^2 is negligible in comparison with R_2. Therefore, T=(K^’ s)/R_2 .
⇒ T α s
∴For low slip region, Torque-slip curve is a straight line.
S2. Ans.(a)
Sol. For normal biasing, the emitter junction of BJT has a low input impedance (emitter junction).
S3. Ans.(b)
Sol.
Drift current arises from the movement of carriers in response to an applied electric field.
The movement of charge carriers from higher concentration to lower concentration generates diffusion current.
S4. Ans.(a)
Sol. Flat compound generator has zero percent regulation.
For Flat compound generator, Vnl=Vfl
S5. Ans.(d)
Sol. current coil has very small resistance. When it is connected in place of the voltage coil, then the whole current will flow through it and will cause damage to the current coil.
S6. Ans.(c)
Sol. A PMMC instruments has linear scale whereas moving iron instrument has non-linear /non-uniform scale.
