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Maharashtra HSC Electronics Field Technician (NSQF F6) study materials
Maharashtra HSC Electronics Field Technician (NSQF F6) study resources

Maharashtra HSC Electronics Field Technician (NSQF F6) practice questions

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Question 1Basic Electricity and Electronic Components

A resistor is marked with the colour bands brown, black, red, gold. What is its nominal value and tolerance?

  1. 1 kΩ ±10%
  2. 100 Ω ±5%
  3. 1 kΩ ±5% Correct answer.
  4. 10 kΩ ±5%

Explanation

Brown = 1, black = 0, red = multiplier ×100, so 10 × 100 = 1000 Ω = 1 kΩ. Gold in the fourth band means ±5% tolerance. The sequence is read from the band nearest the end of the body.

Question 2Basic Electricity and Electronic Components

Which instrument is connected in series with a circuit branch to measure current?

  1. Ammeter Correct answer.
  2. Ohmmeter
  3. Megohmmeter
  4. Voltmeter

Explanation

An ammeter must carry the branch current, so it is placed in series and designed with very low internal resistance to avoid disturbing the circuit. A voltmeter is connected in parallel across the component instead.

Question 3Basic Electricity and Electronic Components

A 12 V supply drives 3 A through a heater element. What is the resistance of the element?

  1. 4 Ω Correct answer.
  2. 36 Ω
  3. 0.25 Ω
  4. 9 Ω

Explanation

Ohm's law gives R = V / I = 12 / 3 = 4 Ω. The element dissipates power P = V × I = 36 W at this operating point.

Question 4Basic Electricity and Electronic Components

Two 100 Ω resistors are connected in parallel. What is the equivalent resistance?

  1. 50 Ω Correct answer.
  2. 25 Ω
  3. 100 Ω
  4. 200 Ω

Explanation

For two equal resistors in parallel the equivalent is half of one value, here 100 / 2 = 50 Ω. The general formula 1/R = 1/R1 + 1/R2 gives the same result.

Question 5Basic Electricity and Electronic Components

In a forward-biased silicon diode, what is the typical barrier voltage needed before appreciable conduction?

  1. About 0.2 V
  2. About 0.7 V Correct answer.
  3. About 5 V
  4. About 50 V

Explanation

A silicon p-n junction needs roughly 0.7 V forward bias to overcome the barrier and conduct significantly. Germanium junctions are lower, near 0.2 to 0.3 V.

Question 6Basic Electricity and Electronic Components

What is the SI unit of capacitance?

  1. Weber
  2. Henry
  3. Farad Correct answer.
  4. Ohm

Explanation

Capacitance is measured in farads, defined as one coulomb of stored charge per volt of potential difference. Practical components are usually rated in microfarads, nanofarads or picofarads.

Question 7Basic Electricity and Electronic Components

Which colour code band position on a four-band resistor indicates the tolerance?

  1. Second band
  2. Fourth band Correct answer.
  3. First band
  4. Third band

Explanation

On a four-band resistor the first two bands give significant digits, the third gives the multiplier, and the fourth gives tolerance. Gold or silver commonly appears in that last position.

Question 8Basic Electricity and Electronic Components

A fuse in a field instrument is rated 500 mA. What does this rating mean?

  1. It limits the voltage to 500 mV
  2. It will open the circuit when current exceeds about 500 mA Correct answer.
  3. It stores 500 mC of charge
  4. It drops exactly 500 mV at any current

Explanation

A fuse rating states the current at which the element melts and interrupts the circuit, protecting wiring and components from overload. It is a current rating, not a voltage or charge rating.

Question 9Basic Electricity and Electronic Components

A 10 kΩ resistor carries 2 mA. What power does it dissipate?

  1. 40 mW Correct answer.
  2. 2 mW
  3. 400 mW
  4. 20 mW

Explanation

Power is I²R = (0.002)² × 10 000 = 0.04 W, which is 40 mW. Checking with V = IR = 20 V and P = VI also gives 40 mW.

Question 10Basic Electricity and Electronic Components

What happens to the total resistance of a circuit when an extra resistor is added in parallel?

  1. It decreases below the smallest branch resistance Correct answer.
  2. It becomes equal to the sum of all resistances
  3. It stays exactly the same
  4. It increases above the largest branch resistance

Explanation

Adding a parallel path gives current another route, so total resistance falls and is always less than the smallest individual branch. In series the opposite is true.

Question 11Basic Electricity and Electronic Components

A capacitor of 10 µF is charged to 50 V. How much charge is stored?

  1. 50 mC
  2. 0.5 mC
  3. 5 µC
  4. 500 µC Correct answer.

Explanation

Charge is Q = C × V = 10 × 10⁻⁶ × 50 = 500 × 10⁻⁶ C, that is 500 µC. The same result is 0.5 mC, but only 500 µC appears among the choices as the exact value.

Question 12Basic Electricity and Electronic Components

In a full-wave bridge rectifier fed from a transformer, how many diodes conduct during each half cycle?

  1. Three
  2. Two Correct answer.
  3. Four
  4. One

Explanation

A bridge rectifier uses four diodes, but in each half cycle only two of them are forward biased and conduct, forming a path through the load. The other two remain reverse biased.

Question 13Basic Electricity and Electronic Components

Why is a Zener diode operated in reverse breakdown in a voltage regulator?

  1. It converts AC to DC directly
  2. It then behaves as a perfect insulator
  3. It produces a fixed current independent of load
  4. Its breakdown voltage stays nearly constant over a range of current Correct answer.

Explanation

In reverse breakdown the Zener holds an almost constant voltage while current varies, which is exactly what a shunt regulator needs. A series resistor limits the current to a safe value.

Question 14Basic Electricity and Electronic Components

What is the purpose of a bleeder resistor across a large filter capacitor in a power supply?

  1. To raise the DC output voltage
  2. To reduce the transformer rating
  3. To increase the ripple voltage
  4. To discharge the capacitor after power is removed Correct answer.

Explanation

A bleeder provides a discharge path so the capacitor does not remain charged at a dangerous voltage after switch-off. It draws a small standing current during normal operation.

Question 15Basic Electricity and Electronic Components

A coil has 200 turns and carries 0.5 A. If the number of turns is doubled while current is halved, what happens to the magnetomotive force?

  1. It stays the same Correct answer.
  2. It doubles
  3. It halves
  4. It becomes four times larger

Explanation

Magnetomotive force is N × I. Doubling N and halving I gives 400 × 0.25 = 100 ampere-turns, the same as 200 × 0.5. The two changes cancel exactly.

Question 16Basic Electricity and Electronic Components

A resistor shows brown, black, orange, gold bands. Which standard E12 value does it represent?

  1. 1 MΩ
  2. 10 kΩ Correct answer.
  3. 1 kΩ
  4. 100 kΩ

Explanation

Brown = 1, black = 0, orange = ×1000, giving 10 × 1000 = 10 000 Ω or 10 kΩ. Gold confirms ±5% tolerance.

Question 17Basic Electricity and Electronic Components

In a series circuit of three resistors, which quantity is the same through every resistor?

  1. Voltage
  2. Power
  3. Current Correct answer.
  4. Resistance

Explanation

A series circuit offers only one path, so the same current flows through every element. Voltage divides across the resistors in proportion to their values.

Question 18Basic Electricity and Electronic Components

A technician measures 230 V across a load drawing 2 A. What is the apparent power?

  1. 460 VA Correct answer.
  2. 115 VA
  3. 920 VA
  4. 230 VA

Explanation

Apparent power is S = V × I = 230 × 2 = 460 VA. For a purely resistive load this also equals the real power in watts.

Question 19Basic Electricity and Electronic Components

A capacitor and a resistor form a series RC circuit. What is the time constant?

  1. R × C Correct answer.
  2. C / R
  3. R + C
  4. R / C

Explanation

The time constant is the product of resistance and capacitance, τ = RC, in seconds when R is in ohms and C in farads. After one time constant the capacitor reaches about 63% of its final voltage.

Question 20Basic Electricity and Electronic Components

A 1 kΩ resistor and a 4 kΩ resistor are in series across 10 V. What voltage appears across the 4 kΩ resistor?

  1. 8 V Correct answer.
  2. 10 V
  3. 2 V
  4. 4 V

Explanation

The divider formula gives V = 10 × 4/(1 + 4) = 8 V. The 1 kΩ resistor drops the remaining 2 V, since current is 2 mA.

Question 21Basic Electricity and Electronic Components

A copper conductor's length is doubled and its cross-sectional area is halved. How does its resistance change?

  1. It becomes half
  2. It becomes four times larger Correct answer.
  3. It stays the same
  4. It doubles

Explanation

Resistance is proportional to length and inversely proportional to area, R = ρL/A. Doubling L doubles R and halving A doubles it again, so the total is four times the original.

Question 22Basic Electricity and Electronic Components

A bridge rectifier's smoothing capacitor is too small for the load current. What is the visible effect on the output?

  1. Ripple frequency halves
  2. DC output rises above peak
  3. Diode drop disappears
  4. Ripple amplitude increases Correct answer.

Explanation

A smaller capacitor stores less charge and discharges more between peaks, so the ripple voltage grows. Increasing the capacitance or reducing load current reduces ripple.

Question 23Basic Electricity and Electronic Components

In a three-resistor network, 2 kΩ and 6 kΩ are in parallel, and their combination is in series with 1 kΩ. What is the total resistance?

  1. 1.5 kΩ
  2. 2.5 kΩ Correct answer.
  3. 9 kΩ
  4. 7 kΩ

Explanation

The parallel pair gives (2 × 6)/(2 + 6) = 1.5 kΩ. Adding the series 1 kΩ gives 2.5 kΩ total.

Question 24Basic Electricity and Electronic Components

A Zener regulator has a 12 V Zener, a 470 Ω series resistor and a 1 kΩ load, fed from 20 V. What current flows through the Zener?

  1. About 29 mA
  2. About 12 mA
  3. About 5 mA Correct answer.
  4. About 17 mA

Explanation

Load current is 12 V / 1 kΩ = 12 mA. Series resistor current is (20 − 12)/470 ≈ 17 mA. The Zener carries the difference, about 5 mA.

Question 25Basic Electricity and Electronic Components

A capacitor is marked 474K. What is its value?

  1. 470 nF Correct answer.
  2. 4.7 µF
  3. 47 nF
  4. 474 pF

Explanation

In the three-digit code the first two digits are significant and the third is the multiplier in picofarads: 47 × 10⁴ pF = 470 000 pF = 470 nF. The letter K indicates ±10% tolerance.

Question 26Basic Electricity and Electronic Components

A field technician needs a component that stores energy in an electrostatic field between two conducting plates separated by a dielectric. Which component performs this function?

  1. Zener diode
  2. Inductor
  3. Piezoelectric crystal
  4. Capacitor Correct answer.

Explanation

A capacitor stores energy as charge on two plates separated by a dielectric, and the stored energy is held in the resulting electric field. The value depends on plate area, plate spacing and the dielectric material.

Question 27Basic Electricity and Electronic Components

A carbon film resistor in a field instrument is rated 0.25 W. The technician must keep its dissipation safely below this rating. Which condition keeps the resistor within its rating?

  1. Current through it is 20 mA with 10 V across it Correct answer.
  2. Voltage across it is 100 V
  3. Voltage across it is 50 V
  4. Current through it is 40 mA

Explanation

Power dissipated equals voltage multiplied by current, so 10 V at 20 mA gives 0.2 W, which is below the 0.25 W rating. Ratings must never be exceeded, and a margin is normally kept for reliability.

Question 28Basic Electricity and Electronic Components

A technician tests a diode with a multimeter set to the diode-test function. In one direction the display reads about 0.6 V; with the probes reversed it reads OL. What does this indicate?

  1. The diode is a good silicon junction diode Correct answer.
  2. The diode is short-circuited
  3. The diode is a germanium diode with high leakage
  4. The diode is open-circuited

Explanation

A forward drop near 0.6 V and an open reading in reverse is the normal signature of a healthy silicon diode. The meter supplies a small test current, so the forward drop appears directly on the display.

Question 29Basic Electricity and Electronic Components

An iron-cored inductor is used as a filter choke in a power supply. Which property of the inductor opposes any change in the current flowing through it?

  1. Its self-induced back EMF Correct answer.
  2. Its dc resistance
  3. Its core saturation level
  4. Its stray capacitance between windings

Explanation

When current through a coil changes, the changing flux induces a back EMF that opposes the change, which is the property called inductance. This is why a choke smooths current ripple in a supply filter.

Question 30Basic Electricity and Electronic Components

A light-dependent resistor (LDR) is used in a field instrument's automatic lamp circuit. Its resistance falls from about 1 MΩ in darkness to about 1 kΩ in bright light. The LDR is connected in series with a fixed 10 kΩ resistor across a steady 12 V supply, and the voltage across the fixed resistor is used as the signal. What happens to that signal voltage when the light level rises from dark to bright?

  1. It falls from about 0.12 V to about 1.1 V
  2. It rises from about 0.12 V to about 10.9 V Correct answer.
  3. It rises from about 1.1 V to about 10.9 V
  4. It remains at 6 V in both conditions

Explanation

The fixed resistor and LDR form a voltage divider, so the voltage across the fixed resistor is 12 V multiplied by 10 kΩ divided by the sum of the two resistances. In darkness that gives about 0.12 V, and in bright light the LDR drops to 1 kΩ and the voltage rises to about 10.9 V. The signal therefore swings upward as illumination increases.

Question 31Electronic Measurement and Test Instruments

Which instrument is the correct choice for directly measuring the forward voltage drop of a silicon diode in a live circuit?

  1. A signal generator set to 1 kHz
  2. A megger set to 500 V
  3. A clamp meter set to AC amps
  4. A digital multimeter set to the diode test or DC volts range Correct answer.

Explanation

A DMM in diode-test mode or on a low DC volts range can display the forward drop (about 0.6 to 0.7 V for silicon) without disturbing the circuit. The other instruments measure insulation resistance, current, or generate signals, none of which read a small DC voltage.

Question 32Electronic Measurement and Test Instruments

On an analog multimeter, the meter pointer rests slightly left of the zero mark on the DC voltage scale when no input is applied. What is the correct first step before making a measurement?

  1. Short the test leads together
  2. Adjust the mechanical zero screw on the meter movement Correct answer.
  3. Rotate the range selector to the highest range
  4. Replace the internal battery

Explanation

A pointer that does not rest at the electrical zero mark with no input indicates a mechanical offset, corrected with the small zero-adjust screw on the meter face. Shorting the leads is the procedure for zeroing the ohms scale, not the voltage scale.

Question 33Electronic Measurement and Test Instruments

A dual-trace CRO displays two signals. The TIME/DIV is 1 ms/div and one full cycle of the input spans 4 divisions. What is the frequency of that signal?

  1. 4 kHz
  2. 25 Hz
  3. 2.5 kHz
  4. 250 Hz Correct answer.

Explanation

Period = 4 div x 1 ms/div = 4 ms. Frequency = 1/period = 1/0.004 s = 250 Hz. Dividing the timebase by the span, or forgetting to convert milliseconds to seconds, gives the wrong results.

Question 34Electronic Measurement and Test Instruments

Why must a CRO probe be compensated before measuring a high-frequency square wave?

  1. To match the probe's capacitive divider to the scope input so the displayed square edges are not rounded or peaked Correct answer.
  2. To convert the probe into a current-sensing device
  3. To raise the brightness of the trace on the CRT
  4. To increase the input impedance of the oscilloscope to exactly 50 ohm

Explanation

A 10:1 probe forms a capacitive divider with the scope input capacitance, and the trimmer is adjusted so the division ratio is frequency-independent. Without correct compensation a square wave shows rounded corners (under-compensated) or overshoot spikes (over-compensated).

Question 35Electronic Measurement and Test Instruments

A technician measures a resistor marked 4.7 kilo-ohm with a DMM and reads 4.68 kilo-ohm. Which statement best interprets this result?

  1. The resistor is faulty and must be replaced
  2. The resistor value must be re-marked to 4.68 kilo-ohm
  3. The DMM is out of calibration because any deviation is a fault
  4. The reading lies within normal tolerance and the resistor is acceptable Correct answer.

Explanation

A 4.7 kilo-ohm resistor with a common 5 percent tolerance may legitimately read anywhere from about 4.465 to 4.935 kilo-ohm. A reading of 4.68 kilo-ohm is within that band, so the component is good and the small difference reflects tolerance plus meter accuracy.

Question 36Electronic Measurement and Test Instruments

When using a clamp meter to measure the current drawn by a single conductor of a two-wire appliance cord, the reading is zero. What is the most likely reason?

  1. The appliance is drawing more current than the meter range
  2. The clamp meter only works on DC circuits
  3. The clamp jaws are closed around both conductors, so the magnetic fields cancel Correct answer.
  4. The conductor insulation prevents any magnetic field from reaching the jaws

Explanation

A clamp meter responds to the net magnetic field of the conductor(s) inside its jaws. Clamping the whole cord encloses the outgoing and return currents, whose fields cancel, giving a near-zero reading. The single conductor must be separated and clamped alone.

Question 37Electronic Measurement and Test Instruments

What does an insulation resistance tester (megger) actually measure when testing a motor winding to earth?

  1. The capacitance between winding turns
  2. The inductance of the winding at 50 Hz
  3. The leakage current driven by a high DC test voltage, displayed as resistance Correct answer.
  4. The DC resistance of the winding copper

Explanation

A megger applies a high DC voltage (commonly 500 V or 1000 V) and measures the tiny leakage current that flows through insulation, then displays the ratio as resistance. A healthy winding shows a very high value, typically in the megohm range or above.

Question 38Electronic Measurement and Test Instruments

A function generator is set to deliver a 1 kHz sine wave, but the CRO shows a distorted waveform with flat tops. Which control on the generator should be checked first?

  1. The frequency range switch
  2. The sweep time control
  3. The output amplitude level Correct answer.
  4. The DC offset control

Explanation

Flat-topped (clipped) sine waves usually mean the generator is driving its output amplifier into saturation, so the amplitude setting is too high for the load. Reducing the output level or checking the load impedance restores a clean waveform.

Question 39Electronic Measurement and Test Instruments

Which measurement setup gives the most accurate reading of a very small resistance such as 0.1 ohm?

  1. A clamp meter on the 2 A range
  2. A megger on the 500 V range
  3. A four-wire (Kelvin) resistance measurement Correct answer.
  4. A two-wire ohmmeter on the 200 ohm range

Explanation

In a four-wire Kelvin measurement, a constant current is forced through the resistor on one pair of leads while the voltage is sensed on a separate pair. Because no significant current flows in the sense leads, lead and contact resistance drop out of the result, which is essential at fractions of an ohm.

Question 40Electronic Measurement and Test Instruments

A digital storage oscilloscope is used to capture a single, fast transient pulse that occurs once. Which acquisition mode is most appropriate?

  1. XY mode
  2. Single-shot trigger mode Correct answer.
  3. Roll mode
  4. Auto trigger mode

Explanation

Single-shot mode arms the scope to capture one event on the trigger and then freeze the display, preserving the transient for inspection. Auto triggering keeps re-arming and can overwrite the event, while roll and XY modes are display formats not suited to capturing a fast single pulse.

Question 41Electronic Measurement and Test Instruments

A Wheatstone bridge is balanced when the galvanometer shows no deflection. What does this condition indicate about the four arms?

  1. All four resistors are equal in value
  2. The supply voltage has dropped to zero
  3. The bridge is drawing maximum current from the source
  4. The ratio of one pair of adjacent arms equals the ratio of the other pair Correct answer.

Explanation

Balance occurs when the potential at the two midpoints is equal, which requires R1/R2 = R3/R4 for the arms arranged in the standard bridge. The arms need not be equal individually; only their ratios must match.

Question 42Electronic Measurement and Test Instruments

A technician needs to check whether a 50 Hz mains supply is present at a socket without making metallic contact. Which instrument is designed for this?

  1. A non-contact voltage tester Correct answer.
  2. A megger
  3. A logic probe
  4. An LCR meter

Explanation

A non-contact voltage tester senses the electric field around a live conductor and indicates presence without touching metal. Meggers, LCR meters and logic probes are intended for insulation, component and digital-logic testing respectively and are not safe or suitable for non-contact mains detection.

Question 43Electronic Measurement and Test Instruments

A DMM set to the 20 mA DC range is accidentally connected across a 12 V battery. What is the likely outcome?

  1. The meter's internal current shunt or fuse may be damaged by the excessive current Correct answer.
  2. The meter displays 12 V correctly
  3. The meter automatically switches to the volts range
  4. The meter reads a small negative current

Explanation

On a current range the meter presents a very low shunt resistance, so connecting it across a voltage source draws a large current limited only by the source and the fuse. This can blow the current-range fuse or damage the shunt; voltage must be measured with the meter in parallel on a volts range.

Question 44Electronic Measurement and Test Instruments

What is the primary purpose of the timebase circuit in an analog oscilloscope?

  1. To generate a sawtooth voltage that sweeps the electron beam horizontally at a known rate Correct answer.
  2. To regulate the CRT heater supply
  3. To amplify the vertical signal before deflection
  4. To provide the calibration square wave at the front panel

Explanation

The timebase produces a linear sawtooth ramp applied to the horizontal deflection plates, moving the beam across the screen at a calibrated rate set by TIME/DIV. The vertical amplifier handles signal amplitude, and the calibrator is a separate circuit.

Question 45Electronic Measurement and Test Instruments

An oscilloscope displays a Lissajous figure that is a straight diagonal line. What does this indicate about the two signals applied to the X and Y inputs?

  1. They differ in frequency by a factor of two
  2. One signal is absent
  3. They are equal in frequency and in phase Correct answer.
  4. They are 90 degrees out of phase

Explanation

A straight line at 45 degrees (or a tilted line) occurs when the two inputs have the same frequency and either zero or 180 degree phase difference. Other phase relationships produce ellipses or circles, and frequency ratios produce more complex closed patterns.

Question 46Electronic Measurement and Test Instruments

Which statement correctly describes the reading obtained when a true-RMS multimeter measures a distorted non-sinusoidal AC waveform?

  1. It reads only the fundamental component
  2. It reads the effective heating value of the waveform Correct answer.
  3. It reads the average value of the waveform
  4. It reads the peak value divided by two

Explanation

A true-RMS meter computes the root-mean-square value, which corresponds to the equivalent DC heating effect of the waveform regardless of its shape. Average-responding meters calibrated for sine waves give errors on distorted waveforms, which is why true-RMS capability matters.

Question 47Electronic Measurement and Test Instruments

A signal generator's output is set to 2 V peak-to-peak. What RMS value would a true-RMS meter display for this sine wave?

  1. 2.0 V
  2. 0.637 V
  3. 0.707 V Correct answer.
  4. 1.414 V

Explanation

For a sine wave, RMS = peak / sqrt(2). A 2 V peak-to-peak signal has a peak of 1 V, so the RMS value is 1/1.414 = 0.707 V. Confusing peak-to-peak with peak is the common source of error.

Question 48Electronic Measurement and Test Instruments

In a digital multimeter, what is the function of the input protection circuitry around the current shunt?

  1. To limit fault current and prevent damage when the meter is misconnected Correct answer.
  2. To provide the reference voltage for the ohms converter
  3. To filter out 50 Hz noise from voltage readings
  4. To increase the resolution of the ADC

Explanation

Fuses and protection components are placed around the current shunt so that an accidental connection across a voltage source does not destroy the shunt or start a fire. They do not improve resolution, filter readings, or supply the ohms reference.

Question 49Electronic Measurement and Test Instruments

A technician observes that a CRO trace is very dim even at high intensity and the focus control has little effect. Which cause is most consistent with these symptoms?

  1. The vertical amplifier gain is set too low
  2. The CRT cathode emission has aged and the electron beam current is weak Correct answer.
  3. The timebase is running too fast
  4. The probe is not compensated

Explanation

Dim traces that cannot be brightened, together with poor focus, point to a worn CRT cathode that can no longer emit sufficient electrons. Amplifier gain, sweep speed and probe compensation affect the size or shape of the display, not the beam brightness.

Question 50Electronic Measurement and Test Instruments

A technician uses a CRO to measure a 1 kHz sine wave and observes that the displayed waveform drifts slowly across the screen from left to right, even though the TIME/DIV setting is correct. Which control adjustment will stop the drift and give a stable display?

  1. Adjust the trigger LEVEL and set the trigger source to the channel carrying the signal Correct answer.
  2. Increase the intensity control until the trace brightens
  3. Reduce the TIME/DIV setting to a faster sweep speed
  4. Switch the input coupling of the channel to AC

Explanation

A waveform that drifts horizontally is not being triggered at a fixed point of the input cycle, so the sweep starts at a random phase each time. Setting the trigger source to the active channel and adjusting the LEVEL so the sweep starts at a consistent point on the waveform locks the display. Correct timebase and coupling alone cannot stabilise the image without a valid trigger.