Basic Electrical Objectives

1. In order for a 30 volt, 90 watt lamp to work properly in a 120 volt supply the required series resister in ohm is
(A) 10 (B) 20
(C) 30 (D) 40 ans 4
2. According to Thévenin's theorem, any linear active network can be replaced by a single voltage source
(A) in series with a single impedance
(B) in parallel with a single impedance
(C) in series with two impedances
(D) in parallel with two impedances
3. The internal resistance of ammeter is
(A) very small (B) very high
(C) infinite (D) zero
4. Hay bridge is used mainly for the measurement of
(A) resistance (B) inductance
(C) conductance (D) capacitance
5. Which of the following is true about series resonance
(A) The reactance becomes zero and impedance becomes equal to resistance
(B) The current in the circuit becomes maximum
(C) The voltage drop across inductance and capacitance cancels each other
(D) All of the above statements are correct
6. A 3-Ф, 4 wire, 400/230 v feeder supplies 3-phase motor and an unbalanced lighting load. In this system
(A) all four wires will carry equal current
(B) neutral wire will carry no current
(C) neutral wire will carry both motor current and lighting load current
(D) neutral wire will carry current only when lighting load is switched on
7. Equalizing connections are required when paralleling two
(A) alternators (B) compound generators (C) series generators (D) both (B) and (C)
8. An ideal transformer is one which
(A) has a common core for its primary and secondary windings
(B) has no losses and magnetic leakage
(C) has core of stainless steel and windings of pure copper metal
(D) has interleaved primary and secondary windings
9. The principle of operation of a 3-phase induction motor is most similar to that of a
(A) synchronous motor (B) repulsion-start induction motor (C) transformer with a shorted secondary
(D) capacitor-start, induction-run motor
10. In the forward region of its characteristic, a diode appears as
(A) an OFF switch (B) a high resistance (C) a capacitor (D) an ON switch
11. The common-emitter forward amplification factor βdc is given by
(A) IC/IE (B) IC/Ib (C) IE/IC (D) IB/IF
12. A common emitter amplifier is characterized by
(A) low voltage gain
(B) moderate power gain
(C) signal phase reversal
(D) very high output impedance
13. After VDS reaches pinch-off value VP in a JFET, drain current IO becomes
(A) zero (B) low (C) saturated (D) reversed
14. An electronic oscillator
(A) needs an external input
(B) provides its own input
(C) is nothing but an amplifier
(D) is just a dc/ac converter
15. In an SCR, the function of the gate is to
(A) switch it off
(B) control its firing
(C) make it unidirectional
(D) reduce forward breakdown voltage
16. NAND and NOR gates are called ‘universal’ gates primarily because they
(A) are available everywhere
(B) are widely used in IC packages
(C) can be combined to produce AND, OR and NOT gates
(D) are the easiest to manufacture
17. Registers and counters are similar in the sense that they both
(A) count pulses
(B) store binary information
(C) are made from an array of flip-flops and gates integrated on a single chip
(D) are in fact shift register
18. A flip-flop
(A) is a sequential logic device
(B) is a combinational logic device
(C) remembers what was previously stored in it
(D) both (A) and (C)
19. An operational amplifier
(A) can be used to sum two or more signals
(B) can be used to subtract two or more signals
(C) uses to principle of feed back
(D) all of the above
20. TTL logic is preferred to DRL logic because
(A) greater fan-out is possible
(B) greater logic levels are possible
(C) greater fan-in is possible
(D) less power consumption is possible
An electron rising through a potential of 250 V will acquire an energy of :
(A) 250 eV
(B) 800 eV
(C) 250 J
(D) 800 J
If the amount of impurity, either donor type or acceptor type added to the intrinsic
semiconductor is controlled to 1 part in one million, the conductivity of the sample :
(A) increases by a factor 103
(B) reduces by a factor 10−3
(C) increases by a factor 106
(D) reduces by a factor 10−6
4. Laplace transform and Fourier integrals are related through :
(A) frequency domain
(B) time domain
(C) both frequency and time domain
(D) none
A clamper circuit :
(i) adds or subtracts a dc voltage to or from a waveform
(ii) does not change the shape of the waveform
(iii) amplifies the waveform
(A) (i) and (ii) are correct
(B) (i) and (iii) are correct
(C) (ii) and (iii) are correct
(D) (i), (ii) and (iii) are correct
A ring counter consisting of five flip flop will have :
(A) 5 states
(B) 10 states
(C) 32 states
(D) infinite states
Which one of the following can be used as parallel to series converter ?
(A) Decoder
(B) Encoder
(C) Digital counter
(D) Multiplexer
An interrupt in which the external device supplies its address as well as the interrupt
request, is known as :
(A) vectored interrupt
(B) maskable interrupt
(C) polled interrupt
(D) non-maskable interrupt
An instruction that can be recognized and used without translation must be written
in :
(A) Source code
(B) Machine code
(C) Basic language
(D) Assembly code
The angle for which there is no reflection and the incident wave is vertically polarized
is known as :
(A) Steradian angle
(B) Reflection angle
(C) Brewster’s angle
(D) Critical angle
A PLL can be used to demodulate :
(A) PAM signals(B) PCM signals(C) PM signals(D) DSB-SC signals
The main function of balanced modulator is to :
(A) produce balanced modulation of a carrier wave
(B) produce 100 percent modulation
(C) suppress carrier signal in order to create a single side band or double side band
(D) limit noise picked up a receiver
An SCR can be termed as :
(A) DC switch(B) AC switch(C) Both DC and AC switch(D) Square wave switch
Fiber optics communication offers the largest bandwidth in the range of :
(A) 1010 Hz(B) 106 Hz(C) 1014 Hz(D) 1020 Hz
Silicon photosensors have their maximum spectral response in the :
(A) infrared region
(B) ultraviolet region
(C) visible region
(D) X-ray region
(1) Instrument is a device for determining
(a) the magnitude of a quantity
(b) the physics of a variable
(c) either of the above
(d) both (a) and (b)
(2) Electronic instruments are preferred because they have
(a) no indicating part
(b) low resistance in parallel circuit
(c) very fast response
(d) high resistance in series circuit
(e) no passive elements.
(3) A DC wattmeter essentially consist of
(a) two ammeters
(b) two voltmeters
(c) a voltmeter and an ammeter
(d) a current and potential transformer
(4) Decibel is a unit of
(a) power
(b) impedance
(c) frequency
(d) power ratio
(5) A dc voltmeter may be used directly to measure
(a) frequency
(b) polarity
(c) power factor
(d)power
(6) An accurate voltmeter must have an internal impedance of
(a) very low value
(b) low value
(c) medium value
(d) very high value
(7) The insulation resistance of a transformer winding can be easily measured with
(a) Wheatstone bridge
(b) megger
(c) Kelvin bridge
(d) voltmeter
(8) A 100 V voltmeter has full-scale accuracy of 5%. At its reading of 50 V it will give an error of
(a) 10%
(b) 5%
(c) 2.5%
(d) 1.25%
(9) You are required to check the p. f. of an electric load. No p.f. meter is available. You would use:
(a) a wattmeter
(b) a ammeter, a voltmeter and a wattmeter
(c) a voltmeter and a ammeter
(d) a kWh meter
(10) The resistance of a field coil may be correctly measured by using
(a) a voltmeter and an ammeter
(b) Schering bridge
(c) a Kelvin double bridge
(d) a Maxwell bridge
(11) An analog instrument has output
(a) Pulsating in nature
(b) Sinusoidal in nature
(c) Which is continuous function of time and bears a constant relation to its input
(d) Independent of the input quantity
(12) Basic charge measuring instrument is
(a) Duddel's oscillograph
(b) Cathode ray oscillograph
(c) Vibration Galvanometer
(d) Bailastic Galvanometer
(e) Battery Charging equipment
(13) A.C. voltage can be measured (using a d.c. instrument) as a value obtained
(a) by subtracting the d.c. reading from it's a.c. reading.
(b) Using the output function of the multimeter
(c) By using a suitable inductor in series with it
(d) By using a parallel capacitor with it
(e) None of the above
(14) A moving coil permanent magnet ammeter can be used to measure
(a) D. C. current only
(b) A. C. current only
(c) A. C. and D. C. currents
(d) voltage by incorporating a shunt resistance
(e) none of these
(15) Select the wrong statement
(a) the internal resistance of the voltmeter must be high
(b) the internal resistance of ammeter must be low
(c) the poor overload capacity is the main disadvantage of hot wires instrument
(d) the check continuity with multimeter, the highest range should be used.
(e) In moving iron voltmeter, frequency compensation is achieved by connecting a capacitor across its fixed coil.
(16) Which of the following instrument is suitable for measuring both a.c. and d.c.
quantities.
(a) permanent magnet moving coil ammeter.
(b) Induction type ammeter.
(c) Quadrant electrometer.
(d) Moving iron repulsion type ammeter.
(e) Moving iron attraction type voltmeter.
(17) Swamping resistance is used in moving coil instruments to reduce error due to
(a) thermal EMF
(b) temperature
(c) power taken by the instrument
(d) galvanometer sensitivity.
(18) A power factor meter is based on the principle of
(a) electrostatic instrument
(b) Electrodynamometer instrument
(c) Electro thermo type instrument
(d) Rectifier type instrument.
(19) A potentiometer recorder is used for
(a) AC singles
(b) DC signals
(c) both (a) and (b)
(d) time varying signals
(e) none of these.
(20) Transformers used in conjunction with measuring instruments for measuring purposes are called
(a) Measuring transformers
(b) transformer meters
(c) power transformers
(d) instrument transformers
(e) pulse transformers.
(21) Leakage flux in an electrical machine is measure by
(a) Ballistic galvanometer
(b) Flux meter
(c) Either (a) or (b)
(d) Vibration galvanometer
(e) CRO
(22) A C.R.O. is used to indicate
(a) supply waveform
(b) magnitude of the applied voltage
(c) B.H. loop
(d) all of these
(e) Magnitude of the current flowing in it.
(23) An oscillator is a
(a) an amplifier having feedback network
(b) a high gain amplifier
(c) a wide band amplifier
(d) a untuned amplifier
(e) None of these
(24) Distortion can be measured by
(a) Wave meter
(b) Digital filters
(c) Wein bridge circuit
(d) Bridge T filter circuit
(25) Series connected Q- meter is preferable for measurement of components having
(a) high impedance
(b) low impedance
(c) both (a) and (b)
(d) high frequency
(e) low capacitance
(26) A potentiometer is
(a) an active transducer
(b) a passive transducer
(c) a secondary transducer
(d) a digital transducer
(e) a current sensing transducer
(27) The basic components of a digital voltmeter are:
(a) A/D converter and a counter
(b) A/D converted and a rectifier
(c) D/A converter and a counter
(d) Ramp generator and counter
(e) Comparator
(28) Which of the following electrical equipment cannot convert ac into dc
(a) diode
(b) converter
(c) transformer
(d) mercury arc rectifier
(29) Voltage measurement are often taken by using either a voltmeter or
(a) an ammeter
(b) an ohmmeter
(c) an oscillator
(d) a watt-meter
(30)The electric device which blocks DC but allows AC is called:
(a) capacitance
(b) inductor
(c) an oscilloscope
(d) a watt-meter
(31 ) The range of an ammeter can be extended by using a
(a) shunt in series
(b) shunt in parallel
(c) multiplier in series
(d) multiplier in parallel
(32)A device that changes one form of energy to another is called
(a) rheostat
(b) oscillator
(c) transducer
(d) varicap
(33) Aquadag is used in CRO to collect
(a) primary electron
(b) secondary electron
(c) both primary and secondary
(d) none of above
(34) A vertical amplifier for CRO can be designed for
(a) only a high gain
(b) only a broad bandwidth
(c) a constant gain time bandwidth product
(d)all of the above
(35) One of the following is active transducer
(a) Strain gauge
(b) Selsyn
(c) Photovoltic cell
(d) Photo emissive cell
(36) The dynamic characteristics of capacitive transducer are similar to those of
(a) low pass filter
(b) high pass filter
(c) band pass filter
(d) band stop filter
(37) Thermocouples are
(a) passive transducers
(b) active transducers
(c) both active and passive transducers
(d) output transducers
(38) The size of air cored transducers as compare to iron core counter part are
(a) bigger
(b) smaller
(c) same
(39) From the point of view of safety, the resistance of earthing electrode should be:
(a) low
(b) high
(c) medium
(d) the value of resistance of electrode does not effect the safety
(40) In CRT the focusing anode is located
(a) between pre accelerating and accelerating anodes
(b) after accelerating anodes
(c) before pre accelerating anodes
(d) none of above
(41) Which transducer converts heat energy into electrical energy
(a) I. V. D. T.
(b) thermocouple
(c) photoconductor
(d) none of the above
(42) Which of photoelectric transducer is used for production of electric energy by converting solar energy
(a) photo emission cell
(b) photo diode
(c) photo transistor
(d) both (b) and (c)
(43) Which of the following instruments consumes maximum power during measurement?
(a) induction instruments
(b) hot wire instruments
(c) thermocouple instruments
(d) electrodynamometer instruments
(44) Which of the following meters has the best accurancy
(a) moving iron meter
(b) moving coil meter
(c) rectifier type meter
(d) thermocouple meter
(45) The function of the safety resistor in ohm meter is to
(a) limit the current in the coil
(b) increase the voltage drop across the coil
(c) increase the current in the coil
(d) protect the battery
(46) Which of the following instruments is free from hysteresis and eddy current losses?
(a) M.l. instrument
(b) electrostatic instrument
(c) electrodynamometer type instrument
(d)all of these
(47) The dielectric loss of a capacitance can be measured by
(a) Wien bridge
(b) Owen bridge
(c) Schering bridge
(d) Maxwell bridge
(48) Reed frequency meter is essentially a
(a) recording system
(b) deflection measuring system
(c) vibration measuring system
(d) oscillatory measuring system
(49) In measurements made using a Q meter, high impedance elements should preferably be connected in
(a) star
(b) delta
(c) series
(d) parallel
(50) A digital voltmeter measures
(a) peak value
(b) peak-to-peak value
(c) rms value
(d) average value