Set 3 of 3 in the Electrical Engineering subject series — 80 solved MCQs taken only from verified past papers and solved sets. Questions shuffle on every attempt, and if you leave in the middle, your picked answers are saved in your own browser so you can continue where you left off. Tap one option per question, then press Check Answers for your score.
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The value of back EMF in a DC motor is maximum at:
Correct answer: No load.
di/dt protection of a thyristor is provided by using:
Correct answer: An inductor (L) in series with the thyristor.
dv/dt protection of a thyristor is provided by using:
Correct answer: An RC snubber across the thyristor.
A cell supplies a current of 0.9 A through an external resistor of 2 ohm and a current of 0.3 A through an external resistor of 7 ohm. The internal resistance of the cell is:
Correct answer: 0.5 ohm.
The back EMF equation of a DC motor is given by:
Correct answer: V = Eb + IaRa.
A semiconductor has which type of bond?
Correct answer: Covalent bond.
The common semiconductor material is:
Correct answer: Silicon.
Emitter and collector are both reverse biased in which region of a transistor?
Correct answer: Cut-off region.
A multilayer device with three terminals is:
Correct answer: TRIAC.
SCR is a:
Correct answer: PNPN device.
The location of the zener breakdown region can be controlled by:
Correct answer: Doping level.
The relationship between supply frequency and synchronous speed is:
Correct answer: f = NsP/120.
The speed of a DC motor is:
Correct answer: Inversely proportional to flux per pole.
The maximum flux produced in the core of a transformer is:
Correct answer: Inversely proportional to supply frequency.
Three resistors of 1 ohm, 2 ohm and 3 ohm are connected in a triangle (delta), and a cell of 1.5 V is connected across the 3 ohm resistor. The total current drawn from the cell is:
Correct answer: 1 A.
Three equal resistors in series dissipate 10 W together. If they are now connected in parallel (across the same supply), the total power dissipated will be:
Correct answer: 90 W.
A shunt DC motor takes a current of 5 A at 100 V supply. Its field resistance is 50 ohm and armature resistance is 0.2 ohm. What will be its rotor output?
Correct answer: 300 W.
Two equal resistors are connected in series with a supply. If these resistors are connected in parallel, the power dissipated will become:
Correct answer: Four times.
The rotor of a synchronous motor is excited with direct current when the motor:
Correct answer: Approaches synchronous speed.
Speed control of a DC motor is commonly done by using:
Correct answer: SCR.
Armature reaction in a DC generator can be increased by increasing:
Correct answer: Armature current.
The current gain of a Darlington pair consisting of Q1 and Q2 is:
Correct answer: B1 x B2.
A crystal diode is used as:
Correct answer: Rectifier.
A crystal diode is a ______ device.
Correct answer: Non-linear.
The current-voltage characteristics of the TRIAC are:
Correct answer: Symmetrical.
A thyristor can be turned on with a minimum input current; that current is called:
Correct answer: Trigger current.
The greatest percentage of heat loss in a DC machine is due to:
Correct answer: Copper loss.
In the two-wattmeter method, if the power factor is 0.5, the reading on one of the two meters is:
Correct answer: 0.
If the power factor in the two-wattmeter method is 1, the readings on the two meters are:
Correct answer: Identical.
A converter in which the controllable switch is turned on and switched off at zero voltage and zero current is called:
Correct answer: Quasi-resonant converter.
In AC, the output of a variable frequency drive (VFD) to the load is:
Correct answer: Variable frequency and adjustable voltage.
In a single phase rotary converter, the number of slip rings will be:
Correct answer: Two.
The rotor of an induction motor rotates:
Correct answer: In the direction of stator flux.
N similar resistors, each of resistance r, are connected in parallel and their total resistance is equivalent to R. If these resistors are now connected in series, what will be the total resistance?
Correct answer: N^2 R.
To increase the range of a voltmeter, we use:
Correct answer: Series multiplier.
For the same rating, the power factor of a single phase induction motor is ______ that of a 3-phase induction motor.
Correct answer: Less than.
A heater of 2000 W and a fan of 1000 W are connected in series. The resistance of the heater is:
Correct answer: Less than that of the fan.
When cells are arranged in series:
Correct answer: EMF increases.
When a number of resistances are connected in parallel, the total resistance is:
Correct answer: Less than the smallest resistance.
The time taken by a diode to change from reverse bias to forward bias is called:
Correct answer: Forward recovery time.
Two lamps, 100 W 200 V and 40 W 200 V, are connected in series. The total resistance will be:
Correct answer: 1400 ohms.
The doping level of a zener diode is ______ that of a crystal diode.
Correct answer: More than.
When resistances are connected in parallel, the current divides itself in:
Correct answer: Inverse ratio of resistance.
The forward voltage drop of a silicon semiconductor is:
Correct answer: 0.7 V.
The ripple factor of a half wave rectifier is:
Correct answer: 1.21.
A clamper circuit consists of a capacitor and a diode. The arrangement of the capacitor and diode with respect to the load is:
Correct answer: Diode is in parallel and capacitor in series.
An induction wattmeter can measure:
Correct answer: AC power only.
Which of the following is not a part of a clamper circuit?
Correct answer: Inductor.
A diode conducts in a positive clipper when:
Correct answer: Vin > Vref.
A permanent magnet moving coil (PMMC) instrument is subjected to 10 A, 50 Hz current. Its reading will be:
Correct answer: 0.
Majority carrier flow takes place in which device?
Correct answer: FET.
In a DC motor, which loss decreases with increase in load?
Correct answer: None of these.
Transformer oil should be free from ____.
Correct answer: Moisture.
The drawback of a feedback system is:
Correct answer: Instability.
Quantization noise depends on ____.
Correct answer: Number of quantization levels.
A flip flop is constructed using ____ gates.
Correct answer: NAND.
Pole shoes of a DC machine are fastened to the pole core by ____.
Correct answer: Countersunk screws.
Brushes on the commutator are shifted from GNP to ____.
Correct answer: Avoid sparking.
In a common base amplifier, output voltage is taken from ____.
Correct answer: Collector.
V = 50 V AC, f = 10 kHz, I = 7.96 mA, then inductance L = ?
Correct answer: 100 mH.
Form factor is the ratio of ____.
Correct answer: RMS value to average value.
The electrode between cathode and anode is called ____.
Correct answer: Grid.
A transformer transforms ____.
Correct answer: Voltage.
A semiconductor device is connected to a battery. Upon changing the polarity of the battery, the current reduces to zero. The device is ____.
Correct answer: P-N junction.
For signals having the same peak value, the RMS value is least for ____.
Correct answer: Triangular.
Form factor is maximum for ____.
Correct answer: Half-wave rectifier.
Q of a tuned circuit refers to the property of ____.
Correct answer: Selectivity.
IBM/360 was a ____ computer.
Correct answer: 3rd generation.
The device that produces a constant voltage (V = E) no matter what current is drawn from it is ____.
Correct answer: Ideal voltage source.
The ladder network used in a D/A converter is ____.
Correct answer: R-2R ladder.
TRIAC is a ____.
Correct answer: Bi-directional device.
Choppers have per-unit ripple maximum at duty cycle (alpha) = ____.
Correct answer: 0.5.
The number of digits in the octal number system is ____.
Correct answer: 8.
Binary of decimal 10 is ____.
Correct answer: 1010.
Binary of 0.6875 is ____.
Correct answer: 0.1011.
____ controls the DC motor speed.
Correct answer: SCR.
Two or more voice circuits can be provided on the same carrier by using ____.
Correct answer: ISB.
The AC motor used for servo applications is ____.
Correct answer: Two phase induction motor.
Greatest possible amplification is obtained in ____ configuration.
Correct answer: Common emitter.
____ field lasts as long as the current is flowing in the circuit.
Correct answer: Magnetic.
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