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Past Questions
High a.c voltage are usually measured with a—
A)
Voltmeter and current transformer
B)
Millivoltmeter and shunt
C)
Voltmeter and multiplier
D)
Voltmeter and potential transformer
High AC voltages measured with voltmeter plus potential transformer for isolation/step-down.
An ideal voltage source should have—
A)
zero source resistance
B)
very high voltage
C)
very low voltage with high current
D)
large ampere
Ideal voltage source maintains V irrespective of load, so source impedance =0.
A modulator is a system to —
A)
separate two frequencies
B)
impressed the information on the radio frequency carrier
C)
extract information from the carrier
D)
amplify the audio frequency signal
Modulator impresses baseband information onto RF carrier.
The limitation of voltage multiplying circuit is that —
A)
the output has high ripple content
B)
high voltage output is difficult to obtain
C)
high output current is difficult to obtain
D)
the size of the capacitors becomes very large
Voltage multiplier provides high voltage at very low current; high current difficult due to poor regulation and ripple.
Piezometer is used to measure —
A)
Very high pressure
B)
Pressure in pipes and channels
C)
Very low pressure
D)
Diffrence of pressure between two points
Piezometer measures static pressure head in pipes/channels for low/moderate pressures.
Which component is commonly used in the output stage in chopper?
A)
Transistor
B)
Capacitor
C)
Resistor
D)
Inductor
Chopper output stage uses transistor/thyristor as fast switching device.
The disadvantage of FM over AM is that —
A)
Noise is very high for high frequency signal
B)
Larger bandwidth is required
C)
High modulating power is required
D)
High output power is required
FM requires much larger bandwidth (~200 kHz) vs AM (~10 kHz).
The superposition theorem is applicable to —
A)
Current only
B)
Voltage only
C)
Power only
D)
Current, Voltage and Power
The superposition theorem applies to linear circuits and can be used to find the contribution of each independent source to any branch response. Since voltage and current are linear quantities, superposition is directly applicable to them. Power is not linear (it depends on the square of voltage or current), so it cannot be superposed directly; power must be calculated after finding the total voltage or current. Therefore, among the given choices, the intended correct option is d (Current, Voltage and Power), though strictly speaking superposition is valid for current and voltage, not directly for power. The options a and b are incomplete because the theorem is not limited to only current or only voltage. Option c is incorrect because power is not directly applicable under superposition.
Transformers work on the principle of
A)
self induction
B)
mutual induction
C)
faraday’s law of electromagnetic induction
D)
self and mutual induction
Transformer operates on mutual induction (Faraday's law) between coupled coils.
A passive network has —
A)
no emf source
B)
no current source
C)
neither emf nor current source
D)
has emf but no current source
A passive network is one that does not contain any independent energy source. Therefore, it has neither an emf source nor a current source. Option (c) is correct. Option (a) is incomplete because a passive network may still contain dependent sources in some contexts, but the standard exam definition is that it has no source at all. Option (b) is incorrect because a network may have an emf source and still no current source, which would not make it passive. Option (d) is incorrect because the presence of an emf source means the network is not passive.
What is a common control method for inverter?
A)
Voltage control
B)
Current control
C)
PWM (pulse width modulation)
D)
Frequency control
PWM is standard method to control inverter output voltage and frequency.
A capacitor of 100 uF is charged to 10V through a resistance of 10 K ohm. It will be fully charged in—
A)
5 sec
B)
0.1 sec
C)
1 sec
D)
0.5 sec
RC=10k*100uF=1s; ~5 time constants =5s for full charge.
A cache in the ARM processor reduces —
A)
memory size
B)
memory access time
C)
monitor size
D)
processor size
Cache reduces average memory access time by storing frequently used data.
In a broadcast receive, the local oscillator is tuned to a frequency higher than the incoming frequency to facilitate —
A)
Image frequency rejection
B)
Easier tracking
C)
Adequate frequency coverage
D)
Noise reduction
Tuning LO higher than signal allows easier ganged tracking across band.
Rating of transformer is given in —
A)
kVAR
B)
kV
C)
kVA
D)
Watt
Transformer rating in kVA as it depends on voltage and current independent of power factor.
Which ARM feature helps prevent a process from accessing memory outside its allocated region?
A)
Memory Mapping
B)
Page Table
C)
Memory Protection Unit (MPU)
D)
Address Space Layout Randomization (ASLR)
Memory Protection Unit prevents access outside allocated region.
The major advantage of a pre-selector stage in a receiver is that it provides —
A)
Higher selectivity
B)
Higher fidelity
C)
Better linearity
D)
Larger Band pass
Pre-selector provides front-end selectivity and image frequency rejection.
The filter required to abtain SSB and DSB signal is —
A)
Low pass filter
B)
High pass filter
C)
Band stop filter
D)
Band pass filter
Band-pass filter selects desired sideband(s) to obtain SSB/DSB signals.
In communication system the massage comes from —
A)
Coder
B)
Decoder
C)
Source
D)
Receiver
In communication model, message originates from source.
What is the typical response time of PLC?
A)
Micro second
B)
Milisecond
C)
Second
D)
2 second
Typical PLC scan/response time is in milliseconds (1-10ms).
Varactor is a—
A)
Non-linear resistor
B)
Variable resistor
C)
Non-linear capacitor
D)
Non-linear inductor
Varactor/varicap is voltage-dependent non-linear capacitor used for tuning.
In a VSI (Voltage source inverter) —
A)
the internal impedance of the DC source is negligible
B)
the internal impedance of the DC source is very very high
C)
the internal impedance of the AC source is negligible
D)
the IGBTs are fired at 0 degrees
VSI has stiff DC source with negligible internal impedance to maintain voltage.
The meter used for measuring electrical power is called —
A)
kWh meter
B)
Voltmeter
C)
Ammeter
D)
Wattmeter
Wattmeter measures electrical power; kWh measures energy.
What is the meaning of inverter efficiency?
A)
The ratio of a.c output to d.c power input
B)
The total power loss
C)
The speed of inverter operation
D)
Voltage regulation capability
Efficiency = AC output power / DC input power ratio.
Which of the following circuit is used for timing purposes?
A)
Astable multivibrator
B)
Bistable multivibrator
C)
Monostable multivibrator
D)
Very stable multivibrator
A monostable multivibrator is used for timing purposes because it has one stable state and one temporary quasi-stable state. When triggered, it produces a single output pulse of a predetermined duration, which makes it suitable for time-delay and timing circuits. Astable multivibrators are not timing circuits in this sense because they have no stable state and continuously oscillate, so they are used as oscillators. Bistable multivibrators have two stable states and are used as flip-flops or memory elements, not for generating timed pulses. "Very stable multivibrator" is not a standard multivibrator type in this context and is not the correct answer.