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Red Seal Instrumentation and Control Technician study materials
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Red Seal Instrumentation and Control Technician practice questions

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Question 1Occupational Skills and Safety

Before working on a 480 V motor control centre, an instrumentation technician must verify isolation. Which practice correctly confirms the circuit is de-energized before touching conductors?

  1. Test the circuit with a meter rated for the voltage, then re-test the meter on a known live source Correct answer.
  2. Touch the conductor briefly with the back of a gloved hand to check for voltage
  3. Rely on the breaker handle position shown as OFF on the panel label
  4. Ask a coworker to stand by while the panel door is opened

Explanation

Safe isolation requires proving the tester on a known live source, testing the isolated circuit, and re-proving the tester afterward. This confirms the instrument itself is functioning so a false zero reading cannot be mistaken for a de-energized circuit.

Question 2Occupational Skills and Safety

In a plant using the CSA Z462 arc flash standard, which factor most directly determines the incident energy a technician could be exposed to at a panel?

  1. The gauge of the wire feeding the panel
  2. The number of spare terminals inside the enclosure
  3. The available fault current and the clearing time of the protective device Correct answer.
  4. The colour coding of the panel enclosure

Explanation

Incident energy rises with both the magnitude of fault current and how long the protective device takes to clear the arc. A high available fault current cleared quickly may produce less energy than a lower current that persists.

Question 3Occupational Skills and Safety

A technician must enter a confined space to calibrate a level transmitter. Which condition must be satisfied before entry under typical jurisdictional confined space rules?

  1. The space has been ventilated only after the technician begins work
  2. The supervisor signs the permit after the work is finished
  3. The technician carries a self-contained breathing apparatus as the only control
  4. A hazard assessment and entry permit are completed and atmospheric testing is acceptable Correct answer.

Explanation

Confined space entry requires a hazard assessment, an entry permit, and atmospheric testing before and during entry. These controls confirm the atmosphere and hazards are understood before anyone enters.

Question 4Occupational Skills and Safety

A technician is calibrating a pressure transmitter mounted on a live process line. Which personal protective equipment selection is most appropriate for the task?

  1. Standard safety glasses and cotton coveralls
  2. No PPE because the transmitter is low voltage
  3. A dust mask and hearing protection only
  4. Face shield, flame-resistant clothing, and gloves matched to the process hazard Correct answer.

Explanation

Working on a live process line exposes the technician to pressure release, chemical spray, and thermal hazards. PPE must be selected from the task hazard assessment, typically including a face shield, FR clothing, and chemically appropriate gloves.

Question 5Occupational Skills and Safety

Which document should a technician consult first to determine the permitted work procedures and required PPE for a specific instrument task?

  1. The vendor's marketing brochure
  2. The instrument's calibration certificate
  3. The plant's electrical single-line diagram
  4. The site's job hazard analysis or safe work procedure Correct answer.

Explanation

A job hazard analysis or safe work procedure identifies the hazards of the specific task and the controls, including PPE and permits. It is the primary document guiding safe execution of the work.

Question 6Occupational Skills and Safety

A technician is about to use a multimeter to measure voltage on an unknown circuit. Which meter setting is the safest first step?

  1. Select the lowest voltage range for best resolution
  2. Select the current measurement mode
  3. Select the highest voltage range available and verify the meter's CAT rating Correct answer.
  4. Select the resistance measurement mode

Explanation

Starting on the highest voltage range and confirming the meter's category rating protects both the technician and the instrument from unexpected high voltage. The CAT rating indicates the meter's ability to withstand transient overvoltages at that point in the installation.

Question 7Occupational Skills and Safety

A technician is asked to work alone on energized 347 V lighting control wiring. Under common electrical safety standards, what is the correct response?

  1. De-energize the circuit or arrange the required energized-work permit and standby person Correct answer.
  2. Proceed if rubber gloves are worn
  3. Refuse all future work on lighting circuits
  4. Proceed alone because 347 V is below 600 V

Explanation

Energized work above limited-energy thresholds generally requires justification, an energized work permit, and often a second qualified person. De-energizing is the preferred control, and working alone on such circuits is normally not permitted.

Question 8Occupational Skills and Safety

During a loop check, a technician notices a strong smell of natural gas near a transmitter. What is the correct immediate action?

  1. Leave the area, avoid operating switches, and initiate the emergency response and gas isolation procedure Correct answer.
  2. Continue the loop check and report the smell at the end of the shift
  3. Increase ventilation by opening windows and continue working
  4. Open the enclosure to locate the leak with a lighter

Explanation

A gas release is an emergency: evacuate, avoid ignition sources such as switches, and activate the site emergency response so the gas can be isolated. Continuing work near a flammable release risks fire or explosion.

Question 9Occupational Skills and Safety

A technician is selecting a replacement fuse for a 24 VDC instrument power supply circuit. Which approach is correct?

  1. Match the voltage rating, current rating, and interrupting rating to the circuit requirements Correct answer.
  2. Bypass the fuse temporarily to confirm the circuit works
  3. Use a fuse of the same physical size regardless of ratings
  4. Install a fuse with a higher current rating to prevent nuisance blowing

Explanation

A fuse must match the circuit's voltage rating, current rating, and interrupting capacity to protect safely. Substituting on size or increasing the rating defeats overcurrent protection and can cause overheating or fire.

Question 10Occupational Skills and Safety

Which practice best protects a technician from stored energy when servicing a hydraulic actuator on an instrument loop?

  1. Rely on the actuator spring to hold the load in position
  2. Close the supply valve and immediately disconnect the tubing
  3. Loosen the fitting slowly to let pressure escape during removal
  4. Isolate, bleed trapped pressure to zero, and verify with a gauge before disassembly Correct answer.

Explanation

Stored hydraulic energy must be isolated, bled to zero, and verified before components are opened. Verification with a gauge confirms no residual pressure remains, preventing sudden release or movement.

Question 11Occupational Skills and Safety

A technician must confirm that a safety instrumented function has been properly proof-tested. Which activity best demonstrates this?

  1. Checking that the transmitter display reads ambient temperature
  2. Recording the loop's tag number in the maintenance log
  3. Injecting a simulated process signal and confirming the final element achieves the safe state Correct answer.
  4. Reviewing the instrument's purchase order

Explanation

A proof test verifies the entire safety function from sensor through logic to final element by simulating a trip and confirming the safe state is reached. This detects hidden failures that normal operation would not reveal.

Question 12Occupational Skills and Safety

When using a two-wire 4-20 mA loop, which condition indicates the transmitter is drawing current correctly during normal operation?

  1. The loop current reads 24 mA continuously
  2. The loop current stays at 0 mA regardless of process
  3. The loop current varies between 4 mA and 20 mA with the process variable Correct answer.
  4. The loop voltage equals the supply voltage at all times

Explanation

In a two-wire loop the transmitter modulates loop current between 4 mA at zero and 20 mA at full scale. Current outside this range, such as 0 mA or above 20 mA, typically signals a fault or saturation.

Question 13Occupational Skills and Safety

A technician is preparing to work on a transmitter installed in a Class I, Division 2 area. Which precaution is most relevant?

  1. Open the enclosure freely because Division 2 areas are always safe
  2. Use only non-sparking tools and ignore the area classification
  3. Work only at night when the process is shut down
  4. Ensure the area is de-energized and confirm the area classification permit before opening the enclosure Correct answer.

Explanation

Class I, Division 2 areas can contain ignitable concentrations under abnormal conditions, so work must follow the area classification and permit requirements. De-energizing and confirming the classification controls ignition risk.

Question 14Occupational Skills and Safety

A technician is using a ladder to reach a ceiling-mounted instrument. Which practice is correct?

  1. Carry tools in both hands while climbing
  2. Have a coworker hold the ladder while the technician leans outward
  3. Maintain three points of contact and keep the ladder on stable footing Correct answer.
  4. Stand on the top two rungs to reach higher

Explanation

Ladder safety requires stable footing, three points of contact, and avoiding overreaching. These practices prevent falls, which are a leading cause of workplace injury in instrument work.

Question 15Occupational Skills and Safety

A technician must dispose of a spent calibration gas cylinder and used solvent rags. Which action is correct?

  1. Follow the site's hazardous waste procedures and label and segregate the materials Correct answer.
  2. Place both in the regular shop waste bin
  3. Store the rags in an open container near the workbench
  4. Pour the solvent down the drain and discard the cylinder in scrap metal

Explanation

Solvent-contaminated rags and pressurized cylinders are regulated wastes that require labelling, segregation, and disposal per site procedures. Improper disposal can cause fire, environmental release, or regulatory violations.

Question 16Occupational Skills and Safety

A technician is troubleshooting a control panel and finds a capacitor that may retain charge. What is the correct safety step?

  1. Assume the capacitor is discharged because the power is off
  2. Short the terminals with a screwdriver to discharge it quickly
  3. Discharge the capacitor using an approved method and verify zero voltage before touching Correct answer.
  4. Wait five seconds and then handle the terminals

Explanation

Capacitors can retain dangerous charge after power is removed, so they must be discharged with an approved method and verified at zero volts. This prevents shock or arc flash during troubleshooting.

Question 17Occupational Skills and Safety

Which action best demonstrates a technician's obligation to work within their scope of practice?

  1. Sign off on work performed by others without review
  2. Perform any repair needed to keep the plant running
  3. Modify safety instrumented functions without approval
  4. Decline tasks outside their training and refer them to a qualified tradesperson Correct answer.

Explanation

Working within scope means performing only tasks for which the technician is trained and qualified, and referring others to the appropriate trade. This protects workers and the integrity of safety systems.

Question 18Occupational Skills and Safety

A technician is calibrating a transmitter in a hot, noisy compressor room. Which combination of hazards should the job hazard analysis address?

  1. Only the noise exposure
  2. Only the instrument accuracy
  3. Heat stress, noise exposure, and electrical hazards Correct answer.
  4. Only the electrical hazard

Explanation

A job hazard analysis must consider all credible hazards of the task and environment, including heat stress, noise, and electrical exposure. Addressing only one hazard leaves workers unprotected from the others.

Question 19Occupational Skills and Safety

Before energizing a newly installed instrument loop, which verification is most important for safety?

  1. Confirm the wiring, grounding, and terminations match the drawings and are secure Correct answer.
  2. Confirm the loop was installed on schedule
  3. Confirm the instrument's serial number is recorded
  4. Confirm the vendor shipped the correct colour

Explanation

Verifying wiring, grounding, and terminations against the drawings prevents shorts, ground loops, and shock hazards before energization. This check confirms the installation is safe and correct before power is applied.

Question 20Occupational Skills and Safety

A technician is working near an operating conveyor while calibrating a sensor. Which control is most appropriate to prevent entanglement?

  1. Work quickly to minimize exposure time
  2. Rely on the conveyor's warning horn
  3. Lock out and tag out the conveyor before reaching near moving parts Correct answer.
  4. Wear loose clothing to stay cool

Explanation

Lockout and tagout isolates the conveyor's energy so moving parts cannot start while the technician is near them. Warning devices and speed do not prevent unexpected startup or entanglement.

Question 21Tools, Materials and Equipment

A technician is preparing to install a new pressure transmitter in an area classified as Zone 1, Group IIB. Which enclosure marking is suitable for this location?

  1. Ex o IIA T3 Gb
  2. Ex nA IIB T4 Gc
  3. IP66 only
  4. Ex d IIB T4 Gb Correct answer.

Explanation

Zone 1 requires equipment with an Equipment Protection Level of Gb or higher, and the gas group must match or exceed IIB. Flameproof 'Ex d' with group IIB and a T-class rating satisfies both the EPL and gas-group requirements. An IP rating alone says nothing about ignition protection.

Question 22Tools, Materials and Equipment

When bending a length of 1/2-inch stainless steel instrument tubing, why is a lever-type tube bender preferred over a spring bender?

  1. It supports the tube walls to prevent flattening and kinking at the bend. Correct answer.
  2. It allows the tubing to be bent without any annealing of the material.
  3. It produces bends with a larger radius than a spring bender can achieve.
  4. It permits bending of tubing that has already been filled with process fluid.

Explanation

A lever bender uses a formed shoe that wraps the tube and a follower that supports the outside of the bend, keeping the cross-section round. Stainless tubing work-hardens and kinks easily, so this support is essential for a clean bend. Spring benders offer less control and are generally used on softer copper.

Question 23Tools, Materials and Equipment

A calibrated 4-20 mA loop is being checked with a handheld loop calibrator set to source current. Where should the calibrator be connected to inject a simulated transmitter signal while the loop is energized?

  1. In series with the loop while the existing transmitter remains connected
  2. In series with the loop after disconnecting the transmitter's positive lead Correct answer.
  3. Across the receiver input terminals while the loop supply is switched off
  4. In parallel across the transmitter terminals with the loop power removed

Explanation

To simulate a transmitter, the calibrator sources current into the loop in place of the transmitter, so the transmitter's signal lead must be lifted and the calibrator inserted in series. The loop supply stays on so the receiver sees the injected current. Leaving the transmitter connected would put two current sources in parallel and corrupt the reading.

Question 24Tools, Materials and Equipment

Which instrument is used to measure the concentration of a specific gas in a confined space before personnel enter?

  1. Rotameter
  2. Hygrometer
  3. Gas detector Correct answer.
  4. Manometer

Explanation

A gas detector, often a multi-gas meter, senses combustible or toxic gas concentration and oxygen level to confirm the space is safe for entry. Manometers measure pressure, rotameters measure flow, and hygrometers measure humidity, none of which indicate gas concentration.

Question 25Tools, Materials and Equipment

A technician needs to verify the output of a thermocouple without a reference junction at 0 degrees C. Which instrument function compensates for the cold-junction temperature?

  1. A loop calibrator sourcing 4-20 mA
  2. A millivoltmeter with a manual offset dial
  3. An ohmmeter measuring the thermocouple resistance
  4. A thermocouple simulator with internal cold-junction compensation Correct answer.

Explanation

A thermocouple simulator with cold-junction compensation measures the ambient temperature at its terminals and adds the equivalent thermoelectric voltage so the output matches a true 0 degrees C reference. Without compensation the injected millivoltage would be offset by the terminal temperature. A plain millivoltmeter cannot correct for this automatically.

Question 26Tools, Materials and Equipment

What is the primary purpose of a seal pot (diaphragm seal) on a pressure transmitter measuring a corrosive process fluid?

  1. To isolate the transmitter from the process fluid via a fill fluid Correct answer.
  2. To dampen process pulsations mechanically
  3. To amplify the process pressure for better resolution
  4. To convert gauge pressure into absolute pressure

Explanation

A diaphragm seal places a flexible diaphragm between the process and the transmitter, with a fill fluid transmitting the pressure. This keeps corrosive or viscous fluid out of the transmitter's sensing element and capillary. It does not amplify pressure or change the pressure reference.

Question 27Tools, Materials and Equipment

A technician is selecting a signal cable to run a 4-20 mA analog signal through an area with high electrical noise. Which cable construction best rejects induced noise?

  1. Coaxial cable with the shield grounded at both ends
  2. Twisted pair with an overall shield grounded at one end Correct answer.
  3. Parallel conductors with no shield
  4. Single-conductor unshielded wire

Explanation

Twisting the pair causes induced noise to cancel because the loops see equal and opposite voltages, and a shield grounded at one end drains interference without creating a ground loop. This combination is standard practice for analog current loops. Grounding a shield at both ends can create circulating currents.

Question 28Tools, Materials and Equipment

Which test instrument is used to check the insulation resistance of a field wiring run before energizing a new loop?

  1. Megohmmeter Correct answer.
  2. Oscilloscope
  3. Clamp meter
  4. Decade box

Explanation

A megohmmeter applies a high DC test voltage to measure insulation resistance and reveal degraded or damaged insulation. Clamp meters measure current, oscilloscopes view waveforms, and decade boxes provide reference resistance, none of which test insulation integrity.

Question 29Tools, Materials and Equipment

A technician must torque the flange bolts on a high-pressure transmitter manifold to a specified value. Which tool provides the most controlled and repeatable tightening?

  1. An impact wrench
  2. A standard open-end wrench
  3. A calibrated torque wrench Correct answer.
  4. A pipe wrench

Explanation

A calibrated torque wrench releases or indicates at a set torque, giving repeatable and even clamping force across the bolt pattern. Even tightening prevents gasket damage and leakage. Impact and standard wrenches offer no controlled torque value.

Question 30Tools, Materials and Equipment

A technician is choosing a multimeter to troubleshoot a 24 VDC control circuit. Which setting should be selected to measure the voltage across an energized coil?

  1. DC volts with the meter in parallel with the coil Correct answer.
  2. Resistance with the circuit energized
  3. Continuity with the circuit energized
  4. DC amps with the meter in series with the coil

Explanation

Voltage is measured across a component, so the meter goes in parallel with the coil on the DC volts range. Measuring current requires breaking the circuit and placing the meter in series. Resistance and continuity functions must never be used on an energized circuit.

Question 31Tools, Materials and Equipment

Which material is commonly selected for instrument air supply tubing because it resists corrosion and is easy to bend without special tools?

  1. Cast iron
  2. Copper tubing Correct answer.
  3. Black iron pipe
  4. Galvanized rigid conduit

Explanation

Soft copper tubing is widely used for instrument air because it bends readily, joins with flare or compression fittings, and resists corrosion in clean air service. Black iron and cast iron are rigid and prone to internal corrosion, and rigid conduit is for electrical wiring.

Question 32Tools, Materials and Equipment

A technician is installing a thermowell in a pipeline and must choose the mounting method. Which arrangement allows the sensor to be removed for service without draining the line?

  1. A welded closed-end thermowell threaded into the pipe
  2. A flanged thermowell with a sealing gland that allows the sensor to withdraw Correct answer.
  3. A surface-mounted clamp-on sensor
  4. A bare thermocouple inserted through a packed gland with no well

Explanation

A flanged thermowell provides a pressure-tight barrier between the process and the sensor, so the element can be withdrawn through the well's sealing arrangement while the line stays pressurized. The well itself remains in the pipe. Welded, surface-mounted, and bare-probe arrangements do not offer this isolation.

Question 33Tools, Materials and Equipment

Which type of valve is best suited for tight shutoff and throttling control of a clean liquid in an instrument loop?

  1. Check valve
  2. Globe valve Correct answer.
  3. Gate valve
  4. Butterfly valve

Explanation

A globe valve's contoured plug and seat give good throttling characteristics and reliable shutoff, making it a common choice for control service on clean fluids. Gate valves are for isolation, butterfly valves suit large-bore on/off duty, and check valves allow flow in one direction only.

Question 34Tools, Materials and Equipment

A technician is troubleshooting a 4-20 mA loop that reads a constant 4 mA regardless of process change. Which tool configuration best isolates whether the transmitter or the loop wiring is at fault?

  1. A loop calibrator set to read current, placed in series with the transmitter Correct answer.
  2. An oscilloscope connected to the controller's analog input
  3. A decade box inserted in place of the transmitter
  4. A megohmmeter connected across the transmitter terminals

Explanation

Placing a loop calibrator in read mode in series with the transmitter shows the actual current the transmitter is producing. If the transmitter output changes while the controller input does not, the fault is in the wiring or receiver. The other tools do not directly compare transmitter output to loop behavior.

Question 35Tools, Materials and Equipment

Which document defines the tag number, range, and location of every field instrument in a plant and is essential when planning an installation?

  1. Instrument index Correct answer.
  2. Loop diagram
  3. Material safety data sheet
  4. Piping and instrumentation diagram (P&ID)

Explanation

The instrument index is a master list that records each instrument's tag, service, range, location, and related data, making it the primary reference for installation planning. A P&ID shows process relationships, a loop diagram details one circuit's wiring, and an MSDS covers chemical hazards.

Question 36Tools, Materials and Equipment

A technician is calibrating a differential pressure transmitter used for level measurement on a closed tank with a wet leg. What must be done to account for the static head of the wet-leg fill?

  1. Apply a zero elevation (suppression) offset during calibration Correct answer.
  2. Increase the transmitter's damping setting
  3. Reverse the transmitter's mA output polarity
  4. Reduce the span to half the nominal range

Explanation

The wet leg exerts a constant pressure on the high side that does not correspond to level, so the transmitter's zero must be suppressed by that head to read correctly. This is done by applying a zero elevation offset. Damping, polarity, and span changes do not correct for static head.

Question 37Tools, Materials and Equipment

Which fitting is used to connect a small-diameter instrument tube to a threaded port with a metal-to-metal ferrule seal?

  1. Compression fitting Correct answer.
  2. Union fitting
  3. Flare fitting
  4. Bushing

Explanation

A compression fitting uses a ferrule that is crushed onto the tube as the nut is tightened, creating a metal-to-metal seal. Flare fittings use a flared tube end, unions join two tube ends, and bushings adapt thread sizes.

Question 38Tools, Materials and Equipment

A technician is selecting a flowmeter for a clean, low-viscosity liquid where a direct volumetric reading and low pressure drop are desired. Which meter type fits best?

  1. Positive displacement meter
  2. Turbine flowmeter Correct answer.
  3. Coriolis mass flowmeter
  4. Vortex shedding meter

Explanation

A turbine flowmeter gives a volumetric reading from rotor speed with relatively low pressure drop on clean, low-viscosity liquids. Positive displacement meters are better for viscous fluids, Coriolis meters measure mass and cost more, and vortex meters need sufficient velocity and can be affected by low flow.

Question 39Tools, Materials and Equipment

A technician is wiring a 2-wire 4-20 mA transmitter to a PLC analog input card. Which statement correctly describes the power and signal path?

  1. The transmitter uses four wires, two for power and two for a voltage output.
  2. The input card supplies loop power and the transmitter modulates current through the same two wires. Correct answer.
  3. The input card measures voltage across a resistor while the transmitter supplies its own isolated power.
  4. The transmitter supplies loop power to the input card.

Explanation

In a 2-wire loop, the analog input card or a separate loop supply provides DC power, and the transmitter varies the current drawn through the same pair to represent the measurement. The receiver converts that current to a voltage across a sense resistor. A 2-wire device does not supply its own isolated power.

Question 40Tools, Materials and Equipment

A technician must replace a fuse in an instrument panel and the original marking is illegible. Which action is the correct practice?

  1. Install a slow-blow fuse of any rating that fits the holder
  2. Bypass the fuse temporarily to restore operation
  3. Replace it with a fuse of the same voltage and current rating as specified in the panel documentation Correct answer.
  4. Install a fuse with a higher current rating to prevent nuisance blowing

Explanation

A replacement fuse must match the specified voltage and current rating to protect the circuit as designed. Oversizing or bypassing removes protection and can cause overheating or fire. The panel documentation or schematic is the authority for the correct rating.

Question 41Electrical and Electronic Fundamentals

In a series circuit, three resistors of 10 Ω, 20 Ω, and 30 Ω are connected across a 12 V supply. What is the current through the 20 Ω resistor?

  1. 0.20 A Correct answer.
  2. 0.60 A
  3. 1.20 A
  4. 0.40 A

Explanation

In a series circuit the total resistance is the sum of the individual resistances, 10 + 20 + 30 = 60 Ω, so the supply current is 12 V ÷ 60 Ω = 0.20 A. The same current flows through every element of a series loop, so the 20 Ω resistor also carries 0.20 A.

Question 42Electrical and Electronic Fundamentals

Which statement describes the voltage across components connected in parallel?

  1. It equals the sum of the branch voltages.
  2. It is zero across the lowest-resistance branch.
  3. It is the same across each branch. Correct answer.
  4. It divides in proportion to branch resistance.

Explanation

Parallel branches share the same two nodes, so the potential difference across each branch is identical and equals the source voltage. Current, not voltage, divides between the branches.

Question 43Electrical and Electronic Fundamentals

A 100 Ω resistor dissipates 4 W. What is the voltage across it?

  1. 400 V
  2. 20 V Correct answer.
  3. 25 V
  4. 40 V

Explanation

Power is P = V²/R, so V = √(P·R) = √(4 W × 100 Ω) = √400 = 20 V. Checking: 20² ÷ 100 = 4 W, confirming the result.

Question 44Electrical and Electronic Fundamentals

Which unit correctly expresses electrical conductance?

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

Explanation

Conductance, the reciprocal of resistance, is measured in siemens (S), where 1 S = 1 A/V. The ohm measures resistance, the farad capacitance, and the henry inductance.

Question 45Electrical and Electronic Fundamentals

What is the primary function of a bridge rectifier in an instrument power supply?

  1. Smoothing ripple to a steady direct voltage
  2. Regulating the output against load changes
  3. Converting alternating current to pulsating direct current Correct answer.
  4. Stepping the supply voltage down

Explanation

A bridge rectifier uses four diodes to conduct both half-cycles of the AC input in the same direction, producing pulsating DC. Filtering, regulation, and voltage transformation are performed by separate stages.

Question 46Electrical and Electronic Fundamentals

Which property of a capacitor opposes a change in voltage across it?

  1. It stores magnetic flux and resists current change.
  2. It dissipates energy as heat proportional to current.
  3. It stores charge and resists sudden voltage change. Correct answer.
  4. It blocks direct current while passing steady voltage.

Explanation

A capacitor stores energy in an electric field, so its terminal voltage cannot change instantaneously; the current is proportional to the rate of change of voltage. This makes it resist abrupt voltage changes and oppose steady DC after charging.

Question 47Electrical and Electronic Fundamentals

What does the term 'root mean square' describe when applied to an alternating voltage?

  1. The instantaneous value at the zero crossing
  2. The average value of the waveform over one full cycle
  3. The effective value that produces the same heating as an equivalent DC voltage Correct answer.
  4. The peak-to-peak amplitude of the waveform

Explanation

The RMS value of a sinusoidal voltage equals the DC voltage that would produce the same power dissipation in a resistive load, which is why it is the standard measure for AC instrumentation. For a sine wave it equals the peak divided by √2.

Question 48Electrical and Electronic Fundamentals

Two resistors of 6 Ω and 3 Ω are connected in parallel. What is the equivalent resistance?

  1. 2 Ω Correct answer.
  2. 4.5 Ω
  3. 18 Ω
  4. 9 Ω

Explanation

For two resistors in parallel, R = (R1 × R2)/(R1 + R2) = (6 × 3)/(6 + 3) = 18/9 = 2 Ω. The result is always less than the smallest branch resistance, which confirms 2 Ω.

Question 49Electrical and Electronic Fundamentals

A coil draws 0.5 A from a 24 V DC supply. What is its resistance?

  1. 24 Ω
  2. 48 Ω Correct answer.
  3. 12 Ω
  4. 0.02 Ω

Explanation

With steady direct current the coil behaves purely resistively, so R = V/I = 24 V ÷ 0.5 A = 48 Ω. Inductive reactance plays no part under DC conditions once the current is steady.

Question 50Electrical and Electronic Fundamentals

A 12 V zener diode with a 6 V rating is used in a shunt regulator. Which condition must hold for regulation to be maintained?

  1. The input voltage must remain above the zener voltage by the required drop across the series resistor. Correct answer.
  2. The zener must be forward biased during normal operation.
  3. The load current must exceed the zener current at all times.
  4. The series resistor must be removed to allow full current.

Explanation

A shunt zener regulator needs the input to stay high enough that the series resistor drops the excess voltage while the zener holds its rated voltage. If the input falls too close to or below the zener voltage, regulation is lost.