UPPCL-JE’21 EE: Daily Practices Quiz 01-Nov-2021

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UPPCL-JE’21 EE: Daily Practices Quiz

UPPCL-JE’21 EE: Daily Practices Quiz 01-Nov-2021

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

Q1. ………. at a point due to a charge distribution is the work done per unit charge when it is moved from infinity to that point.
(a) Electric current
(b) Resistance
(c) Potential
(d) Conductivity

Q2. Which of the following is the property of an ideal operational amplifier?
I. It should have an infinite input impedance.
II. It should have a zero-output impedance.
(a) Only I
(b) Only II
(c) Both I and II
(d) Neither I nor II

Q3. Which of the following statement is correct for the transformer?
I. It transfers electric energy from one circuit to another without a conducting link.
II. It converts energy without the change in frequency.
III. It is a combination of electrical circuits linked by common magnetic circuit.
(a) I and II
(b) I and III
(c) II and III
(d) I, II and III

Q4. A 200 KV transmission line has a maximum power transfer capacity of P. if it is operated at 100 KV with the series reactance unchanged, then its power transfer capacity is approximately
(a) P
(b) P/4
(c) 2P
(d) P/2

Q5. In 3-phase induction motor maximum torque is inversely proportional to the
(a) Speed of rotor
(b) Stator voltage
(c) Decreasing slip speed
(d) Rotor reactance

Q6. A centrifugal switch is provided for disconnecting the auxiliary winding in a
(a) Capacitor start motor
(b) Capacitor run motor
(c) Hysteresis motor
(d) Reluctance motor

SOLUTIONS

S1. Ans.(c)
Sol. Potential at a point due to a charge distribution is the work done per unit charge when it is moved from infinity to that point.
i.e., V=W/q.

S2. Ans.(c)
Sol. Properties of an ideal OP-AMP:
Infinite Input Resistance
Zero Output Impedance
Infinite Open-loop Gain
Infinite Common-mode Rejection Ratio
Infinite Bandwidth

S3. Ans.(d)
Sol. A transformer is defined as a passive electrical device that transfers electrical energy from one circuit to another through the process of electromagnetic induction. It is most commonly used to increase (‘step up’) or decrease (‘step down’) voltage levels between circuits. As the transformer is a Static device or both windings are at standstill, Frequency does not change in Transformer.

S4. Ans.(b)
Sol. Pm=V^2/X
As series reactance unchanged,
∴Pmax α V^2
∴P2=P1×(V2/V1 )^2=P×(100/200)^2=P/4

S5. Ans.(d)
Sol. In 3-phase induction motor: T(max ) α 1/X2

S6. Ans.(a)
Sol. In case of capacitor start motor, a centrifugal switch is provided for disconnecting the auxiliary winding when the motor attains speed up-to 70-80% of synchronous speed.