Electronic Practice

⭕️ Show all Answers

Q1: Which resistor is used to measure light intensity?

• VDR
• NTC
• PTC
• LDR

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Q2: Which code indicates silicon semi conductor diode?

• OA 79
• BY 126
• IN 4007
• 2N 3055

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Q3: What is the input ripple frequency (F) of full wave rectifier?

• $F = \frac{1}{2} F_{in}$
• $F = F_{in}$
• $F = 2F_{in}$
• $F = \sqrt{2}F_{in}$

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Q4: Which is a active component?

• Inductor
• Resistor
• Capacitor
• Transistor

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Q5: Which letter indicates the compound material cadmium sulphide?

• A
• B
• C
• R

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Q6: What is the name of the symbol?

• Two input OR gate
• Two input AND gate
• Two input NOR gate
• Two input NAND gate

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Q7: Which is a passive component?

• Diac
• Diode
• Transistor
• Capacitor

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Q8: What is the name of the device symbol?

• SCR
• IGBT
• DIAC
• TRIAC

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Q9: How many characters are in hexadecimal number system?

• 6
• 8
• 12
• 16

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Q10: Which electronic circuit generates A.C signal without input?

• Filter circuit
• Rectifier circuit
• Amplifier circuit
• Oscillator circuit

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Q11: Which instrument provides a visual representation of measured or tested quantities?

• Voltage stabilizer
• Function generator
• Cathode ray oscilloscope
• Radio frequency generator

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Q12: What is the name of amplifier?

• Common emitter amplifier
• Class B push pull amplifier
• Common collector amplifier
• Class AB push pull amplifier

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Q13: What is the formula to calculate the resonance frequency in an oscillator circuit?

• $F_r = \frac{1}{2LC}$
• $F_r = \frac{1}{\sqrt{2LC}}$
• $F_r = \frac{1}{2\pi\sqrt{LC}}$
• $F_r = \frac{LC}{2\pi}$

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Q14: What is the minimum voltage required in the base emitter junction to conduct a silicon transistor?

• 0.2 V - 0.3 V
• 0.4 V - 0.5 V
• 0.6 V - 0.7 V
• 0.8 V - 0.9 V

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Q15: What is the minimum and maximum value of resistor with four colour bands, red, violet, orange and gold respectively?

• 237500 - 262500
• 247000 - 273000
• 256500 - 283500
• 224000 - 336000

Show Resistance Calculator

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Q16: What is the reason for barrier voltage is more in silicon material?

• Lower atomic number
• Resistance is very low
• Doping percentage is more
• Valance electrons are two only

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Q17: What is the reason for widened barrier in a reverse biased diode?

• Minority carriers in two materials are neutralised
• Electron in N material is drifted to positive terminal
• Holes in P material attracted to negative terminal
• Electrons and holes are attracted towards supply terminals

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Q18: What is the output voltage in the full wave rectifier circuit?

• No output
• Rated output
• Half the rated output
• Double the rated output

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Q19: Which filter circuit is capable of removing voltage spikes in the rectifier circuit?

• LC filter
• RC filter
• Capacitor input filter
• Series inductor filter

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Q20: Which is the advanced version of power electronic component used in the output stage in drives?

• FET
• UJT
• SCR
• IGBT

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Q21: How the decimal number can be converted into binary number?

• Divide decimal by 4
• Multiplying decimal by 4
• Dividing decimal by 2
• Multiplying decimal 2

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Q22: What is the purpose of using binary coded decimal (BCD) system in digital circuits?

• Storing the data inputs
• Control the binary system
• Interface to binary system
• Segregating the input parameters

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Q23: Which logic gate refers the truth table?

• OR gate
• NOT gate
• AND gate
• NOR gate

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Q24: Which quantity can be measured by CRO?

• Frequency
• Inductance
• Resistance
• Power factor

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Q25: Which is the main application of SCR?

• Amplifier
• Oscillators
• Multi vibrators
• Speed control of motors

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Q26: What is the function of R1 variable resistor?

• Controls the current in R1
• Protects from overload to TRIAC
• Protects the RFI filter from overloading
• Controls the pulse rate for triggering the TRIAC

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Q27: What is the purpose of connecting L1 through C1 to the transistor base?

• Provides DC supply
• Provides positive feedback
• Provides negative feedback
• Provides transistor biasing voltage

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Q28: What is the criteria to decide a material as conductor, semi conductor and insulator?

• Atomic bonding structure of atom
• Existence of valance electrons in atom
• Atomic weight of the atom of the material
• Atomic number of the atom of the material

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Q29: Which doping material is used to make P-type semi conductor?

• Boron
• Arsenic
• Antimony
• Phosphorous

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Q30: Which type of biasing is required to a NPN transistor for amplification?

• Base ground, emitter and collector positive
• Base negative, emitter positive and collector negative
• Base positive, emitter negative and collector positive
• Base positive, emitter negative and collector negative

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Q31: What is the type of function in the transistor circuit?

• Switching
• Oscillation
• Modulation
• Amplification

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Q32: Why negative feedback is required in amplifier circuits?

• To reduce the distortion
• To increase the amplification factor
• To increase the output voltage gain
• To increase the output current gain

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Q33: What is the purpose of DIAC in power control circuits?

• As rectifier
• For triggering
• As an oscillator
• For amplification

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Q34: Which type of control device is used in electronic fan regulator control circuits?

• FET
• UJT
• DIAC
• TRIAC

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Q35: Which quadrant operation of SCR delivers heavy current in reverse biasing?

• First quadrant
• Third quadrant
• Fourth quadrant
• Second quadrant

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Q36: Which logic gate refers the truth table?

• AND
• NOT
• NOR
• NAND

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Q37: What is the use of timebase control switch or knob in the CRO?

• Select sweep speed
• Select input voltage range
• Select input signal voltage
• Select intensity of the beam

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Q38: Why a snubber circuit is used in the TRIAC motor control circuit?

• To avoid false triggering
• To increase the life of TRIAC
• To increase the motor torque
• To maintain the motor speed constant

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Q39: What is the output DC voltage in half wave rectifier, if the input AC voltage is 24 volt?

• 24 Volt
• 12 Volt
• 9.6 Volt
• 10.8 Volt

Show Calculation

$V_{dc} = \frac{V_{max}}{\pi}$ Input AC Voltage ($V_{rms}$) = $24 \text{ V}$ $V_{max} = V_{rms} \times \sqrt{2}$ $V_{max} = 24 \times 1.414$ $V_{max} = 33.936 \text{ V}$ $V_{dc} = \frac{33.936}{\pi}$ $V_{dc} = \frac{33.936}{3.1416}$ $V_{dc} \approx 10.8 \text{ V}$ **Short Method:** $$V_{dc} = 0.45 \times 24 = 10.8 \text{ V}$$

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Q40: Why most of semi conductor devices are made by silicon compared to germanium?

• High barrier voltage
• High resistance range
• High thermal conductivity
• High current carrying capacity

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Q41: What is the output voltage if the centre tap of transformer is open circuited in a full wave rectifier circuit?

• Zero voltage
• Full rated output
• Half of the rated output
• One fourth of rated output

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Q42: Which oscillator provides high accurate stable frequency?

• Hartley oscillator
• Colpitts oscillator
• Quartz crystal oscillator
• R.C phase shift oscillator

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Q43: What is the characteristic property of base material in a transistor?

• Lightly doped and very thin
• Heavily doped and very thin
• Lightly doped and very larger
• Heavily doped and very larger

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Q44: What is the type of amplifier?

• Push Pull Amplifier
• Common Base Amplifier
• Emitter Follower Amplifier
• Common Emitter Amplifier

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Q45: Which resistor determines the voltage gain in a common emitter amplifier?

• $R_1$
• $R_2$
• $R_L$
• $R_e$

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Q46: Which multi vibrator produces a repetitive pulse wave form output?

• Astable multi vibrator
• Bistable multi vibrator
• One shot multi vibrator
• Monostable multi vibrator

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Q47: Why a feedback network is used in the oscillator?

• To cancel noise distortion
• To phase shift the signal by 60°
• To phase shift the signal by 180°
• To cancel second harmonic distortion

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Q48: What is the main application of a Field Effect Transistor (FET)?

• Voltage control device
• Current control device
• Positive feedback device
• Low input impedance device

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Q49: What is the main function of Uni Junction Transistor (UJT)?

• Relaxation oscillator
• Broadcast transmitter
• Loud speaker amplifier
• Microphone input device

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Q50: How the gate terminal of N channel JFET biased?

• Gates are reverse biased
• Gates are forward biased
• Gates are forward biased with drain
• Gates are reverse biased with source

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Q51: What is the total turn-on time ($t_{on}$) while transistor makes a transition from $V_2$ to $V_1$?

• $t_{on} = t_r - t_d$
• $t_{on} = t_r \times t_d$
• $t_{on} = t_d + t_r$
• $t_{on} = t_d / t_r$

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Q52: Which device is made up of using the methods of point contact, grown, diffusion and alloy junctions?

• Inductor
• Resistor
• Capacitor
• Transistor

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Q53: Why the collector region is physically made larger than emitter region in a transistor?

• It has to dissipate more heat
• Output taken from collector terminal
• Base collector region is reverse biased
• Collector region always operate with high voltage

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Q54: What is the function of a transistor if emitter to base and collector to base are forward biased?

• Acts as an amplifier
• Acts as an oscillator
• Acts as an open circuit
• Acts as a closed switch

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Q55: What is the main advantage of a class A amplifier?

• Minimum distortion
• Maximum current gain
• Maximum voltage gain
• Minimum signal to noise ratio losses

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Q56: Which electronic circuit produces signal waves or pulses without an input?

• Detector
• Amplifier
• Oscillator
• Modulator

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Q57: Which circuit is essential to maintain oscillations or waves in an oscillator circuit?

• Rectifier with filter
• Voltage multiplier
• Negative feed back
• Positive feed back

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Q58: What is the main application of uni junction transistor?

• Rectification
• Amplification
• Regulator circuits
• Triggering circuits

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Q59: Which device has very high input impedance, low noise output, good linearity and low inter electrode capacity?

• NPN transistor
• PNP transistor
• Field effect transistor
• Uni junction transistor

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Q60: What is the difference in current control of MOSFET compared to JFETs?

• Insulating layer instead of junction
• Using N material instead of P material
• Using P material instead of N material
• Using N material gate instead of P material

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Q61: What is the type of amplifier circuit?

• Common base amplifier
• Common emitter amplifier
• Class B push pull amplifier
• Common collector amplifier

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Q62: What is the peak voltage of 220V rms AC voltage?

• 310.02 V
• 311.17 V
• 312.25 V
• 315.20 V

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Q63: How the input impedance of CRO can be increased?

• By adding resistance to CRO probe
• By adding resistance to trigger level circuit
• By increasing time/base attenuator switch position
• By increasing volts/cm attenuator switch position

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Q64: What is the frequency of the displayed signal on CRO screen covered by 5 division with a time base setting of 0.2 micro seconds?

• 1.0 KHz
• 10.0 KHz
• 100.0 KHz
• 1000.0 KHz

Show Calculation

$T = \text{Number of divisions} \times \text{Time base setting}$ $F = \frac{1}{T}$ * Number of divisions = $5$ * Time base setting = $0.2 \text{ } \mu\text{s/div}$ (microseconds) $T = 5 \times 0.2 \text{ } \mu\text{s}$ $T = 1.0 \text{ } \mu\text{s}$ $T = 1.0 \times 10^{-6} \text{ seconds}$ $F = \frac{1}{1.0 \times 10^{-6}}$ $F = 1,000,000 \text{ Hz}$ $F = 1000 \text{ kHz}$

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Q65: What defect will occur in the radio, if the pulsations are not removed from the input of the rectifier?

• Improper tuning
• No response
• Humming sound
• Works with low volume

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Q66: How does the depletion region behave?

• As resistor
• As insulator
• As conductor
• As semi conductor

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Q67: What is the power gain of CE amplifier with a voltage gain of 66 and $\beta$ (Beta) of the transistor is 100?

• 1.5
• 166
• 0.66
• 6600

Show Calculation

The Power Gain ($A_p$) of a Common Emitter (CE) amplifier is the product of its Voltage Gain ($A_v$) and Current Gain ($A_i$). For a CE configuration, the current gain is approximately equal to the transistor's Beta ($\beta$). $A_p = A_v \times A_i$ $A_p \approx A_v \times \beta$ * Voltage Gain ($A_v$) = $66$ * Transistor Beta ($\beta$) = $100$ $A_p = 66 \times 100$ $A_p = 6600$

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Q68: What is the effect, if SCR is latched into conduction and gate current is removed in DC?

• SCR gets cut off
• Current through SCR OFF
• Output voltage will be reduced
• Gate looses control over conduction

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Q69: What is the effect of pinch-off voltage in JFET?

• No depletion region exists
• Drain current becomes zero
• Reverse bias voltage becomes zero
• Width of channel has maximum value

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