Electrical Engineering MCQs for Test Preparation Free PDF Download
Electrical Engineering MCQs for Test Preparation Free PDF Download
 
The sum of all phase current in a star connected primary winding with no neutral connection is equal to___________?
A. Phase current
B. Three times the phase current
C. Three times the line current
D. Zero at all times
In a load commutated DC – DC chopper, the capacitor has a_____________?
A. Symmetric triangular voltage across itself
B. Symmetric rectangular voltage across itself
C. Symmetric trapezoidal voltage across itself
D. Symmetric sinusoidal voltage across itself
In a 3 phase bridge rectifier the ripple frequency is _____________?
A. Equal to the input frequency
B. Twice the input frequency
C. Three times the input frequency
D. Six times the input frequency
The average value of the output voltage in a step – down dc chopper is given by__________?
A. V 0 = V s
B. V 0 = D V s
C. V 0 = V s / D
D. V 0 = V s / ( 1 – D )
Between the incoming and outgoing devices in voltage commutation
A. Large overlapping takes place
B. Small overlapping operation
C. No overlapping operation
D. None of these
The control method used for PWM dc – dc converter is______________?
A. Voltage mode control
B. Current mode control
C. Hysteric control
D. All of these
During the commutation period in 3 phase converter, overlap time is_____________?
A. Dependent on the load current
B. Dependent on the voltage
C. Dependent on both the load current and load voltage behind the short circuit current
D. Independent on both the load current and load voltage
The main objective of static power converters is to____________?
A. Obtain an dc output waveform from a dc power supply
B. Obtain an ac output waveform from a dc power supply
C. Obtain an dc output waveform from a dc power supply
D. Obtain an ac output waveform from a ac power suppl
In a three phase converter, the number of notches per cycle is____________?
A. One
B. Three
C. Six
D. Nine
A capacitive load in voltage source inverters generates ________________?
A. Small current spikes and can be reduced by using an inductive filter
B. Large current spikes and can be increased by using an inductive filter
C. Small current spikes and can be increased by using an inductive filter
D. Large current spikes and can be reduced by using an inductive filter
In a 3 phase CSI, if the required line output voltages are balanced and 120 degree out of phase, then the chopping angles are used to eliminate only the harmonics at frequencies
A. 5
B. 7
C. 11
D. All of these
The carrier which are commonly used in constant – frequency PWM is______________?
A. Sawtooth carrier
B. Inverted sawtooth carrier
C. Triangle carrier
D. All of these
For similar carrier and modulating signals, the line current used in CSI is__________?
A. Identical to line voltage in a VSI
B. Identical to line current in VSI
C. Identical to phase voltage in VSI
D. Identical to phase voltage in CSI
Double edge modulation eliminates certain harmonics when the reference is a__________?
A. Sine wave
B. Square wave
C. Triangular wave
D. Trapezoidal wave
Under harmonic free load voltages, the 3 phase VSI_____________?
A. Does not contains second harmonic
B. Does not contains third harmonic
C. Does not contains fifth harmonic
D. Does not contains seventh harmonic
In a three phase voltage source inverters____________?
A. Only amplitude of voltage is controllable
B. Only phase is controllable
C. Both amplitude and phase is controllable
D. Amplitude, phase and frequency of voltages should always be controllable
The square wave operation of 3 phase VSI lines contains the harmonics. The amplitudes are____________?
A. Directly proportional to their harmonic order
B. Inversely proportional to their harmonic order
C. Not related to their harmonic order
D. None of these
In a 3 phase VSI out of eight valid states, the number of valid states that produce zero ac line voltages is/are_________?
A. One
B. two
C. Three
D. Four
In bipolar modulation, the carrier is symmetric about zero with amplitude equal to Cm, the PWM output
A. Zero
B. Switches between – 1 / 2 and + 1 / 2
C. Switches between – 1 and + 1
D. Switches between 0 and + 1
In the operation and control of both naturally commutated and forced commutated SCR base converter, commutation plays an important role. The converters is / are ___________?
A. AC – DC
B. DC – DC
C. DC – AC
D. All of these
Double fourier series analysis of PWM is_____________?
A. Two dimensional functions
B. Three dimensional functions
C. One dimensional functions
D. All of these
In commutation PAC stands for_______?
A. Permanent angle converter
B. Phase angle converter
C. Phase angle commutation
D. Phase and commutation
In single phase VSI, the harmonic which is not present is____________?
A. 2nd
B. 3rd
C. 5th
D. 7th
Any electrical signal present in a circuit other than the desired signal is known as______________?
A. Noise
B. Distortion
C. Interference
D. All of these
Very large values of modulation index (greater than 3.24) lead to___________?
A. Square AC output voltage
B. Sine AC output voltage
C. Triangular AC output voltage
D. Trapezoidal AC output voltage
The man made noise sources is / are_____________?
A. Motors
B. Switches, radio interferences
C. Computers, digital electronics
D. All of these
Single phase VSI are mainly used in___________?
A. Power supplies
B. Ups
C. Multilevel configuration
D. All of these
Due to non sinusoidal waveform of the input current, the power factor of the rectifier is____________?
A. Negatively affected by firing angle
B. Negatively affected by distortion of the input current
C. Positively affected by both firing angle and distortion of the input current
D. Both (a) and (b)
In rectifiers, load current flow is_________?
A. Unidirectional
B. Bidirectional
C. Either (a) or (b)
D. Non directional
For bidirectional operation of converters____________?
A. A parallel combination of controllable switch and a diode is used
B. A parallel combination of controllable switch and capacitor is used
C. A series combination of controllable switch and a diode is used
D. A series combination of controllable switch and a capacitor is used
Advantages of HVDC transmission over AC system is / are____________?
a. Reversal of power can be controlled by firing angle
b. Very good dynamic behavior
c. They can link two AC system operating unsynchronized
d. All of these
For a buck converter to reduce the conduction losses in diode
A. A high on – resistance switch can be added in parallel
B. A low on – resistance switch can be added in parallel
C. A high on – resistance switch can be added in series
D. A low on – resistance switch can be added in series
The conduction losses in IGBT is____________?
A. More than that of MOSFET
B. Lower than that of MOSFET
C. Equal to that of MOSFET
D. Equal to that of BJT
In dual converters________________?
A. Both rectifiers provides positive current to the load
B. Both rectifiers provide negative current to the load
C. One rectifiers provide positive current to the load and the other negative current
D. One rectifier provide positive current to the source and the other negative current to the load
The power MOSFET device is a___________?
A. Current controlled unipolar device
B. Voltage controlled unipolar device
C. Current controlled bipolar device
D. Voltage controlled bipolar device
n a phase controlled 3 phase ac voltage controller, the harmonic present is__________?
A. 2nd
B. 3rd
C. 5th
D. 7th
With increase in firing angle,
A. Both harmonic distortion and quality of input current increases
B. Harmonic distortion increases and quality of input current decreases
C. Harmonic distortion decreases and quality of input current increases
D. Both harmonic distortion and quality of input current decreases
The maximum firing angle in the half wave controlled regulator is_____________?
A. 180 degree
B. 190 degree
C. 200 degree
D. 210 degree
The most suited gate pulses given to the AC regulator with R – L load can be in the form of____________?
A. Continuous signal
B. Large isolating pulse transformer
C. A train of pulses
D. None of these
The on – state voltage drop of IGBT consists of__________?
A. Drop across the collector junction
B. Drop across the drift region
C. Drop across MOSFET portion
D. All of these
Harmonics in 3 phase inverters can be reduced by using___________?
A. Passive filter
B. Active filter
C. Both passive and active filters
D. None of these
To detect an over – current fault condition, the most reliable method is to connect a_____________?
A. Current sensor across IGBT
B. Voltage sensor across IGBT
C. Current sensor in series with IGBT
D. Voltage sensor in series with IGBT
The advantage of using free – wheeling diode in half controlled bridge converter is that
A. There is always a path for the dc current independent of the ac line
B. There is always a path for the ac current independent of the ac line
C. There is always a path for the dc current dependent of the ac line
D. There is always a path for the ac current independent of the ac line
The IGBT resulted in higher switching speed and lower energy losses. It can be used for___________?
A. Uninterruptible power supplies
B. Induction heating system
C. Constant voltage and frequency power supplies
D. All of these
The input current waveform of a bridge controlled rectifier when the load is perfectly filtered is___________?
A. Sine wave
B. Square wave
C. Saw – tooth wave
D. Trapezoidal wave
An ideal diode is___________?
A. Unidirectional
B. Bidirectional
C. Fixed voltage polarity
D. Only (a) and (c)
A full wave rectifier with resistive load produces___________?
A. Second harmonic
B. Third harmonic
C. Fifth harmonic
D. Do not produce harmonics
Bidirectional semiconductor device is___________?
A. Diode
B. BJT
C. SCR
D. TRIAC
A crowbar is a circuit which is used to protect a_____________?
A. voltage sensitive load from excessive dc power supply output voltages
B. current sensitive load from excessive dc power supply output voltages
C. voltage sensitive load from excessive ac power supply output voltages
D. current sensitive load from excessive ac power supply output voltages
With gate open, the maximum anode current at which SCR is turned off from ON condition is called____________?
A. breakdown voltage
B. peak reverse voltage
C. holding current
D. latching current
An SCR can be used___________?
A. as static conductor
B. for power control
C. for speed control of dc shunt motor
D. All of these
The curve between V and I of SCR when anode is positive w.r.t cathode and when anode is negative w.r.t cathode are known as_____________________?
A. both as forward characteristics
B. both as reverse characteristics
C. former as forward characteristics and later as reverse characteristics
D. former as reverse characteristics and later as forward characteristics
TRIAC is a semiconductor power electronic device which contains____________?
A. Two SCR’s connected in reverse parallel
B. Two SCR’s connected in parallel
C. Two SCR’s connected in series
D. Two BJT’s connected in series
Silicon controlled rectifier can be turned on____________?
A. By applying a gate pulse and turned off only when current becomes zero
B. And turned off by applying gate pulse
C. By applying a gate pulse and turned off by removing the gate pulse
D. By making current non zero and turned off by making current zero
Form factor of a rectifier is the ratio of ______________?
A. Root mean square value of voltage and current to its peak value
B. Root mean square value of voltage and current to its average value
C. Average value of current and voltage to its root mean square value
D. Peak value of current and voltage to its root mean square value
Ripple factor is the ratio of______________________?
A. Rms value of the ac component of load voltage to the dc voltage
B. Average value of the ac component of load voltage to the peak value of voltage
C. Average value of the dc component of load voltage to the ac voltage
D. Peak value of the dc component of load voltage to the ac voltage
In a square – wave operation of 3 phase CSIs, the power values are on for___________?
A. 60 degree
B. 90 degree
C. 120 degree
D. 150 degree
A carrier based PWM technique in CSI is composed of____________?
A. A switching pulse generator and a shorting pulse generator
B. A shorting pulse distributor
C. A switching and shorting pulse combination
D. All of these
Transformer utilization factor is a measure of the merit of a rectifier circuit. It is the ratio of_______________?
A. AC input power to the transformer volt – amp rating required by secondary
B. AC input power to the transformer volt – amp rating required by primary
C. DC output power to the transformer volt – amp rating required by secondary
D. DC output power to the transformer volt – amp rating required by primary
In a 3 phase half wave rectifier, when firing angle is less than 90 degree, then the average dc output voltage becomes__________________?
A. Positive
B. Negative
C. Zero
D. None of these
In variable frequency, PWM gain
A. Phase lead helps to increase the phase margin of the control loop
B. Phase lag helps to increase the phase margin of the control loop
C. Phase lead helps to decrease the phase margin of the control loop
D. Phase lag helps to decrease the phase margin of the control loop
If the firing angle becomes negative, then the rectifier begins to work as_______________?
A. A rectifier
B. An inverter
C. A chopper
D. A regulator
In constant frequency PWM, at perturbation the amplitude of the sinusoidal component is a___________?
A. Linear function
B. Non linear function
C. Constant function
D. None of these
The Graetz bridge makes excellent use of ______________?
A. Current transformer
B. Potential transformer
C. Power transformer
D. SCR
DIAC and TRIAC both are semiconductors devices and conduct in____________________?
A. DIAC conducts in forward direction and TRIAC conducts in reverse direction
B. Both conducts in forward direction
C. Both conducts in reverse direction
D. Both conducts in either direction
The transfer function of PWM is generally developed in______________?
A. Time domain
B. Frequency domain
C. Either A. or B.
D. None of these
A TRIAC can be turned on with______________?
A. Positive voltage at the gate terminal
B. Negative voltage at the gate terminal
C. Either (a) or (b)
D. None of these
In the SPWM, the modulating signal is___________?
A. Square
B. Sinusoidal
C. Triangular
D. Saw – tooth
The phase angle of gate signal in TRIAC can be shifted by using_____________?
A. A capacitor
B. A variable resistor
C. An inductor
D. Only (a) and (b)
In a full bridge VSI, in order to avoid the short circuit across the DC bus and the undefined AC output voltage condition, the modulating technique should ensure that___________?
A. Top switch of each leg is on at any instant
B. Bottom switch of each leg is on at any instant
C. Either A. or B.
D. None of these
The ac voltage controller can be used for ___________?
A. Lighting and heating control
B. On – line transformer tap changing
C. Soft starting
D. All of these
In a lossless inverter, the average power absorbed in one period by the load must be__________?
A. Equal to the average power supplied by the dc source
B. Greater than the average power supplied by the dc source
C. Lesser than the average power supplied by the dc source
D. Equal to the average power supplied by the ac source
A step – down choppers can be used in___________?
A. Electric traction
B. Electric vehicles
C. Machine tools
D. All of these
The output current in PWM DC – DC converters is equal to___________?
A. Average value of the output inductor current
B. Product of an average inductor current and a function of duty ratio
C. Either A. or B.
D. None of these
The opposite of susceptibility is___________?
A. Immunity
B. Emission
C. Interference
D. Electromagnetic compatibility
The ability of an electronic system to function properly in its intended electromagnetic environment and should not be a source of pollution to that electromagnetic environment is known as____________?
A. Susceptibility
B. Emission
C. Interference
D. Electromagnetic compatibility
If all the SCR’s of 3 phase PAC is replaced by diodes, they would be triggered_____________?
A. 120 degree after the zero crossing of the corresponding line voltages
B. 60 degree after the zero crossing of the corresponding line voltages
C. 120 degree before the zero crossing of the corresponding line voltages
D. 60 degree before the zero crossing of the corresponding line voltages
For commutation in three phase PAC, normally balanced three phase voltages VR, VY and VB are connected to the three legs of the converter via______________?
A. Three inductances
B. Three capacitances
C. Three resistance
D. Three transistors
In square wave operation mode of 3 phase VSI, the VSI
A. Can control the load voltage
B. Cannot control the load voltage
C. Cannot control the load voltage except by means of dc link voltage
D. Cannot control the load voltage except by means of dc link current
In a 3 phase VSI SPWM to use a single carrier signal and preserve the features of PWM technique, the normalized carrier frequency should be____________?
A. Multiple of two
B. Odd multiple of three
C. Odd multiple of five
D. Odd multiple of seven
Regulator sampling PWM is usually used in___________?
A. High power inverters
B. Rectifiers
C. Low power inverters
D. Only A. and B.
A combination of synchronized leading edge and trailing edge modulation has also been used to control a____________?
A. Boost single – phase power factor converter
B. A buck dc – dc converter to reduce ripple in the intermediate dc bus capacitor
C. Both A. and B.
D. None f these
If energy is taken from the AC side of the inverter and sends it back into the DC side, then it is known as___________?
A. Motoring mode operation
B. Braking mode operation
C. Regenerative mode operation
D. None of these
The ac output voltage waveform of VSI and AC output current waveform of CSI respectively is composed of___________?
A. High dv / dt, low di / dt
B. Low dv / dt, low di / dt
C. Low dv / dt, high di / dt
D. High dv / dt, high di / dt
An RC snubber network used in BJT__________?
A. Divert the collector current during turn – off
B. Improves the reverse bias safe operating area
C. Dissipates a fair amount of switching power
D. All of these
A MOSFET, for its conduction uses_____________?
A. Only minority carriers
B. Only majority carriers
C. Both minority and majority carriers
D. None of these
Advantages of Cuk converter is / are_____________?
A. Large number of reactive component
B. Low stress on switch
C. Low stress on capacitor
D. None of these
In a flyback converter, the inductor of the buck-boost converter has been replaced by a_____________?
A. Flyback capacitor
B. Flyback resistor
C. Flyback transformer
D. Flyback transistor
MOSFET stands for______________?
A. Metal – oxide semiconductor field effect transistor
B. Molybdenum – oxide semiconductor field effect transistor
C. Metal – oxide silicon field effect transistor
D. Metal – oxide semiconductor field effect transmitter
In a push – pull converter, the filter capacitor can be obtained as____________?
A. Cmin = V / ( Vr L f2 )
B. Cmin= ( 1 – D ) V / ( Vr L f2 )
C. Cmin= ( 1 – 2 D ) V / 32 ( Vr L f2 )
D. Cmin= ( 1 – 2 D ) V / 42 ( Vr L f2 )
Kingdom Protoctista includes_______________?
A. Prokaryotic organisms
B. Unicellular organisms
C. Fungi
D. Eu-cariotiquic organisms
The size of poxvirus is_______________?
A. 20 nm
B. 200 nm
C. 250 nm
D. 300 nm
Electric pressure is also called________?
A. resistance
B. power
C. voltage
D. energy
The substances which have a large number of free electrons and offer a low resistance are called____?
A. insulators
B. inductors
C. semi-conductors
D. conductors
Out of the following which is not a poor conductor__________?
A. Cast iron
B. Copper
C. Carbon
D. Tungsten
Out of the following which is an insulating material____________?
A. Copper
B. Gold
C. Silver
D. Paper
The property of a conductor due to which it passes current is called___________?
A. resistance
B. reluctance
C. conductance
D. inductance
Conductance is reciprocal of____________?
A. resistance
B. inductance
C. reluctance
D. capacitance
The resistance of a conductor varies inversely as___________?
A. length
B. area of cross-section
C. temperature
D. resistivity
With rise in temperature the resistance of pure metals______________?
A. increases
B. decreases
C. first increases and then decreases
D. remains constant
With rise in temperature the resistance of semi-conductors_________________?
A. decreases
B. increases
C. first increases and then decreases
D. remains constant
The resistance of a copper wire 200 m long is 21 Q. If its thickness (diameter) is 0.44 mm, its specific resistance is around_______________?
A. 1.2 x 10~8 Q-m
B. 1.4 x 10~8 Q-m
C. 1.6 x 10″”8 Q-m
D. 1.8 x 10″8 Q-m
An instrument which detects electric current is known as_____________?
A. voltmeter
B. rheostat
C. wattmeter
D. galvanometer
In a circuit a 33 Q resistor carries a current of 2 A. The voltage across the resistor is
A. 33 V
B. 66 v
C. 80 V
D. 132 V
A light bulb draws 300 mA when the voltage across it is 240 V. The resistance of the light bulb is___________?
A. 400 Q
B. 600 Q
C. 800 Q
D. 1000 Q
The resistance of a parallel circuit consisting of two branches is 12 ohms. If the resistance of one branch is 18 ohms, what is the resistance of the other ?
A. 18 Q
B. 36 Q
C. 48 Q
D. 64 Q
Four wires of same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 25 Q. If the same four wires are connected is series the effective resistance will be________?
A. 100 Ω
B. 200 Ω
C. 300 Ω
D. 400 Ω
A current of 16 amperes divides between two branches in parallel of resistances 8 ohms and 12 ohms respectively. The current in each branch is_____________?
A. 6.4 A, 6.9 A
B. 6.4 A, 9.6 A
C. 4.6 A, 6.9 A
D. 4.6 A, 9.6 A
Current velocity through a copper conductor is___________?
A. the same as propagation velocity of electric energy
B. independent of current strength
C. of the order of a few ^.s/m
D. nearly 3 x 108 m/s
Which of the following material has nearly zero temperature co-efficient of resistance_________?
A. Manganin
B. Porcelain
C. Carbon
D. Copper
You have to replace 1500 Q resistor in radio. You have no 1500 Q resistor but have several 1000 Q ones which you would connect__________?
A. two in parallel
B. two in parallel and one in series
C. three in parallel
D. three in series
Two resistors are said to be connected in series when___________?
A. same current passes in turn through both
B. both carry the same value of current
C. total current equals the sum of branch currents
D. sum of IR drops equals the applied e.m.f.
Which of the following statement is true both for a series and a parallel D. C. circuit?
A. Elements have individual currents
B. Currents are additive
C. Voltages are additive
D. Power are additive
Which of the following materials has a negative temperature co-efficient of resistance?
A. Copper
B. Aluminum
C. Carbon
D. Brass
Ohm’s law is not applicable to____________?
A. vacuum tubes
B. carbon resistors
C. high voltage circuits
D. circuits with low current densities
Which is the best conductor of electricity _______________?
A. Iron
B. Silver
C. Copper
D. Carbon
For which of the following ‘ampere second’ could be the unit ?
A. Reluctance
B. Charge
C. Power
D. Energy
All of the following are equivalent to watt except_____________?
A. (amperes) ohm
B. joules/seC.
C. amperes x volts
D. amperes/volt
A resistance having rating 10 ohms, 10 W is likely to be a__________?
A. metallic resistor
B. carbon resistor
C. wire wound resistor
D. variable resistor
Which one of the following does not have negative temperature co-efficient ____________?
A. Aluminium
B. Paper
C. Rubber
D. Mica
Varistors are______________?
A. insulators
B. non-linear resistors
C. carbon resistors
D. resistors with zero temperature coefficient
Insulating materials have the function of______________?
A. preventing a short circuit between conducting wires
B. preventing an open circuit between the voltage source and the load
C. conducting very large currents
D. storing very high currents
Insulating materials have the function of___________?
A. preventing a short circuit between conducting wires
B. preventing an open circuit between the voltage source and the load
C. conducting very large currents
D. storing very high currents
The rating of a fuse wire is always expressed in________________?
A. ampere-hours
B. ampere-volts
C. kWh
D. amperes
The minimum charge on an ion is______________?
A. equal to the atomic number of the atom
B. equal to the charge of an electron
C. equal to the charge of the number of electrons in an atom (#) zero
In a series circuit with unequal resistances______________?
A. the highest resistance has the most of the current through it
B. the lowest resistance has the highest voltage drop
C. the lowest resistance has the highest current
D. the highest resistance has the highest voltage drop
The filament of an electric bulb is made of______________?
A. carbon
B. aluminium
C. tungsten
D. nickel
A 3 Q resistor having 2 A current will dissipate the power of_______________?
A. 2 watts
B. 4 watts
C. 6 watts
D. 12 watts
Which of the following statement is true________________?
A. A galvanometer with low resistance in parallel is a voltmeter
B. A galvanometer with high resistance in parallel is a voltmeter
C. A galvanometer with low resistance in series is an ammeter
D. A galvanometer with high resistance in series is an ammeter
The resistance of a few meters of wire conductor in closed electrical circuit is____________?
A. practically zero
B. low
C. high
D. very high
If a parallel circuit is opened in the main line, the current_______________?
A. increases in the branch of the lowest resistance
B. increases in each branch
C. is zero in all branches
D. is zero in the highest resistive branch
If a wire conductor of 0.2 ohm resistance is doubled in length, its resistance becomes______________?
A. 0.4 ohm
B. 0.6 ohm
C. 0.8 ohm
D. 1.0 ohm
Three 60 W bulbs are in parallel across the 60 V power line. If one bulb burns open_________________?
A. there will be heavy current in the main line
B. rest of the two bulbs will not light
C. all three bulbs will light
D. the other two bulbs will light
The four bulbs of 40 W each are connected in series swift a battery across them, which of the following statement is true_______________?
A. The current through each bulb in same
B. The voltage across each bulb is not same
C. The power dissipation in each bulb is not same
D. None of the above
Two resistances Rl and Ri are connected in series across the voltage source where Rl>Ri. The largest drop will be across______________?
A. Rl
B. Ri
C. either Rl or Ri
D. none of them
A closed switch has a resistance of_____________?
A. zero
B. about 50 ohms
C. about 500 ohms
D. infinity
The hot resistance of the bulb’s filament is higher than its cold resistance because the temperature co-efficient of the filament is___________________?
A. zero
B. negative
C. positive
D. about 2 ohms per degree
The insulation on a current carrying conductor is provided__________?
A. to prevent leakage of current
B. to prevent shock
C. both of above factors
D. none of above factors
The thickness of insulation provided on the conductor depends on_____________?
A. the magnitude of voltage on the conductor
B. the magnitude of current flowing through it
C. both A. and (b)
D. none of the above
Which of the following quantities remain the same in all parts of a series circuit ____________?
A. Voltage
B. Current
C. Power
D. Resistance
A 40 W bulb is connected in series with a room heater. If now 40 W bulb is replaced by 100 W bulb, the heater output will__________
A. decrease
B. increase
C. remain same
D. heater will burn out
In an electric kettle water boils in 10 m minutes. It is required to boil the boiler in 15 minutes, using same supply mains______________?
A. length of heating element should be decreased
B. length of heating element should be increased
C. length of heating element has no effect on heating if water
D. none of the above
An electric filament bulb can be worked from____________?
A. D. C. supply only
B. A. C. supply only
C. Battery supply only
D. All above
Electric current passing through the circuit produces_____________?
A. magnetic effect
B. luminous effect
C. thermal effect
D. chemical effect
E. all above effects
Resistance of a material always decreases if___________?
A. temperature of material is decreased
B. temperature of material is increased
C. number of free electrons available become more
D. none of the above is correct
If the efficiency of a machine is to be high, what should be low __________?
A. Input power
B. Losses
C. True component of power
D. kWh consumed
E. Ratio of output to input
When electric current passes through a metallic conductor, its temperature rises. This is due to__________?
A. collisions between conduction electrons and atoms
B. the release of conduction electrons from parent atoms
C. mutual collisions between metal atoms
D. mutual collisions between conducting electrons
Two bulbs of 500 W and 200 W rated at 250 V will have resistance ratio as________?
A. 4 : 25
B. 25 : 4
C. 2 : 5
D. 5 : 2
A glass rod when rubbed with silk cloth is charged because__________?
A. it takes in proton
B. its atoms are removed
C. it gives away electrons
D. it gives away positive charge
Whether circuit may be AC. or D. C. one, following is most effective in reducing the magnitude of the current?
A. Reactor
B. Capacitor
C. Inductor
D. Resistor
It becomes more difficult to remove_________________?
A. any electron from the orbit
B. first electron from the orbit
C. second electron from the orbit
D. third electron from the orbit
When one leg of parallel circuit is opened out the total current will______________?
A. reduce
B. increase
C. decrease
D. become zero
In a lamp load when more than one lamp are switched on the total resistance of the load_____________?
A. increases
B. decreases
C. remains same
D. none of the above
Two lamps 100 W and 40 W are connected in series across 230 V (alternating). Which of the following statement is correct ?
A. 100 W lamp will glow brighter
B. 40 W lamp will glow brighter
C. Both lamps will glow equally bright
D. 40 W lamp will fuse
In the case of direct current____________?
A. magnitude and direction of current remains constant
B. magnitude and direction of current changes with time
C. magnitude of current changes with time
D. magnitude of current remains constant
When electric current passes through a bucket full of water, lot of bubbling is observeD. This suggests that the type of supply is____________?
A. A. C.
B. D. C.
C. any of above two
D. none of the above
Bulbs in street lighting are all connected in_____________?
A. parallel
B. series
C. series-parallel
D. end-to-end
For testing appliances, the wattage of test lamp should be_____________?
A. very low
B. low
C. high
D. any value
Switching of a lamp in house produces noise in the radio. This is because switching operation produces________?
A. arcs across separating contacts
B. mechanical noise of high intensity
C. both mechanical noise and arc between contacts
D. none of the above
74. Sparking occurs when a load is switched off because the circuit has high_________?
A. resistance
B. inductance
C. capacitance
D. impedance
Copper wire of certain length and resistance is drawn out to three times its length without change in volume, the new resistance of wire becomes__________?
A. 1/9 times
B. 3 times
C. 9 times
D. unchanged
When resistance element of a heater fuses and then we reconnect it after removing a portion of it, the power of the heater will___________?
A. decrease
B. increase
C. remain constant
D. none of the above
A field of force can exist only between_____________?
A. two molecules
B. two ions
C. two atoms
D. two metal particles
A substance whose molecules consist of dissimilar atoms is called____________?
A. semi-conductor
B. super-conducto
C. compound
D. insulator
International ohm is defined in terms of the resistance of________________?
A. a column of mercury
B. a cube of carbon
C. a cube of copper
D. the unit length of wire
Three identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be_________________?
A. 9 times
B. 1/9 times
C. 1/3 times
D. 3 times

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