UPPCL-JE’21 EE: Daily Practices Quiz 04-Nov-2021

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UPPCL-JE’21 EE: Daily Practices Quiz

UPPCL-JE’21 EE: Daily Practices Quiz 04-Nov-2021

Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.

Q1. The B-H curve for……. will be a straight line passing through the origin.
(a) Soft iron
(b) Silicon steel
(c) Hardened steel
(d) Air

Q2. The expression for voltage gains A_v of a positive feedback amplifier is
(a) 1/(1-β)
(b) A/(1-βA)
(c) A/(1+A)
(d) None of these

Q3. Condition of symmetry in Z-parameter representation is
(a) Z11 = Z12
(b) Z11 = Z22
(c) Z12 = Z21
(d) Z12 = Z22

Q4. For a shaded pole induction motor, the direction of rotation of the motor is
(a) From the main pole to the shaded pole
(b) From the shaded pole to the main pole
(c) Either (a) or (b) depending on the voltage
(d) Either (a) or (b) depending on the power factor

Q5. For protection of transformer against all kinds of incipient faults, which relay is used:
(a) Buchholz relay
(b) Earth-fault relay
(c) Over current relay
(d) All of the above

Q6. In a transformer, occurrence of dimensional changes both perpendicular and parallel to the direction of magnetization is referred to as:
(a) Damping
(b) Magnetostriction
(c) Coupling
(d) Oscillation

SOLUTIONS

S1. Ans.(d)
Sol. The B-H curve for air will be a straight line passing through the origin as air is non-magnetic material.
A magnetization curve (or) hysteresis loop (or) B-H loop plots the relationship between the induced magnetic flux density (B) and the magnetizing force or magnetic field strength (H).

S2. Ans.(b)
Sol. Voltage gain (A_v ) for positive feedback
=A/(1-Aβ)

S3. Ans.(b)
Sol. A two-port network is said to be symmetrical if the ports of the two-port network can be interchanged without changing the port voltages and currents. This will hold good, if Z11 = Z22.

S4. Ans.(a)
Sol. The shaded pole motor rotates only in one particular direction, and the reverse movement of the motor is not possible. The direction of rotation of the magnetic field is from the main (unshaded) pole to the shaded pole.

S5. Ans.(a)
Sol. Buchholz relay is used for protection against insulation failure of windings, core heating, fall of oil level etc.

S6. Ans.(b)
Sol. magnetostriction is property of ferromagnetic material. By applying magnetic field causes them to expand or contract which is necessary for conversion of electromagnetic energy into mechanical energy.