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PRC EPLE practice questions

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Question 1Electronics Engineering (PRC regulated profession)

According to the PRC Regulations on the Administration of Surveying and Mapping Qualifications, a surveying and mapping qualification grade certificate is valid for how many years from the date of issuance?

  1. 10 years
  2. 8 years
  3. 5 years Correct answer.
  4. 3 years

Explanation

The surveying and mapping qualification grade certificate is issued with a validity period of five years, after which the holder must apply for renewal review before continuing to undertake surveying and mapping activities.

Question 2Electronics Engineering (PRC regulated profession)

In a PRC electronics engineering design file, which document formally records the design basis, technical route, and key parameter selections for review and approval?

  1. The construction log
  2. The commissioning record
  3. The design description (design specification) Correct answer.
  4. The material acceptance certificate

Explanation

The design description is the document that states the design basis, technical route, selected parameters, and design criteria so that reviewers and downstream disciplines can verify compliance. Construction logs and commissioning records are produced later during construction and testing, and acceptance certificates relate to materials rather than design decisions.

Question 3Electronics Engineering (PRC regulated profession)

A regulated electronics design drawing must be signed by the responsible designer and checked by a reviewer. Which principle of the PRC engineering quality responsibility system does this signature chain implement?

  1. Transfer of liability to the contractor
  2. Collective anonymity of the design team
  3. Voluntary self-certification without oversight
  4. Traceable individual responsibility for design quality Correct answer.

Explanation

The signature chain ties each drawing to named individuals so that design quality responsibility can be traced to the designer and reviewer. This supports accountability throughout the project lifecycle rather than diffusing responsibility or shifting it to the constructor.

Question 4Electronics Engineering (PRC regulated profession)

In an electronics schematic, a resistor is marked 4R7. What resistance does this denote?

  1. 4.7 kilohms
  2. 4.7 ohms Correct answer.
  3. 470 ohms
  4. 47 ohms

Explanation

The letter R marks the decimal position in the resistance value, so 4R7 means 4.7 ohms. This convention avoids misreading a small decimal point on printed drawings.

Question 5Electronics Engineering (PRC regulated profession)

Which document type in PRC engineering practice is prepared by the design entity to answer technical queries raised by the construction party about a drawing?

  1. Design clarification (design reply) Correct answer.
  2. Design change notice
  3. Completion acceptance report
  4. As-built drawing

Explanation

A design clarification, often called a design reply, is issued by the designer to explain or confirm intent when the construction party raises a technical query. A design change notice alters the design itself, whereas as-built drawings and acceptance reports belong to later project stages.

Question 6Electronics Engineering (PRC regulated profession)

A PCB trace carrying 3 A continuous current is being sized for a 10 degrees Celsius temperature rise on 1 oz copper. Which design action is most appropriate?

  1. Increase the copper thickness or trace width to lower current density Correct answer.
  2. Route the trace through a series ferrite bead
  3. Reduce the trace width to save board area
  4. Remove the ground plane beneath the trace

Explanation

Trace heating depends on current density, so widening the trace or using thicker copper lowers resistance per unit length and reduces the temperature rise. Narrowing the trace or removing adjacent copper would raise thermal stress, and a ferrite bead does not reduce DC current.

Question 7Electronics Engineering (PRC regulated profession)

Under PRC regulations, which entity bears primary responsibility for the quality of a construction project as a whole during the construction phase?

  1. The material supplier
  2. The supervising entity
  3. The construction contractor Correct answer.
  4. The design entity

Explanation

The construction contractor bears primary responsibility for construction quality, while design, supervision, and suppliers bear responsibility for their own scope. Supervision verifies compliance but does not replace the contractor's primary quality obligation.

Question 8Electronics Engineering (PRC regulated profession)

What is the primary purpose of a residual current device (RCD) in a low-voltage distribution circuit?

  1. Correct the power factor of inductive loads
  2. Detect earth-leakage current and disconnect the circuit Correct answer.
  3. Stabilize the output voltage under load changes
  4. Limit short-circuit current magnitude

Explanation

An RCD monitors the difference between live and neutral currents, which indicates earth leakage, and trips to protect people from electric shock. Short-circuit current limitation, power-factor correction, and voltage stabilization are functions of other protective or compensation devices.

Question 9Electronics Engineering (PRC regulated profession)

An electronics design entity holds a Class B surveying and mapping qualification for a project requiring Class A capability. What is the compliant course of action?

  1. Subcontract the whole project to an unqualified party
  2. Proceed and rely on the client to accept the risk
  3. Upgrade to the required grade before undertaking the work Correct answer.
  4. Issue a design clarification to extend the scope

Explanation

A qualification grade defines the scope of work an entity may lawfully perform, so the entity must first obtain the required grade through the upgrade process. Undertaking work beyond the grade, delegating to unqualified parties, or papering over the gap with clarifications violates the qualification rules.

Question 10Electronics Engineering (PRC regulated profession)

A design change to an approved electronics system increases the rated breaking capacity of a switchgear assembly. What must occur before the change is implemented on site?

  1. The change is recorded only in the as-built drawings
  2. The change is reviewed and approved through the design change procedure before construction Correct answer.
  3. The contractor decides independently whether to apply the change
  4. The change is implemented and documented afterwards

Explanation

Design changes affecting safety-relevant ratings must pass through the formal review and approval procedure before execution so that all disciplines can verify impacts. Retrospective documentation or unilateral contractor decisions bypass the quality control chain.

Question 11Electronics Engineering (PRC regulated profession)

A 24 V DC power supply feeds a load 60 m away through copper cable with a loop resistance of 0.14 ohms per 100 m. If the load draws 2 A, what is the approximate voltage at the load terminals?

  1. 23.83 V
  2. 22.40 V
  3. 24.00 V
  4. 23.66 V Correct answer.

Explanation

The total loop length is 120 m, so the loop resistance is 0.14 times 1.2, equal to 0.168 ohms. The drop is 2 A times 0.168 ohms, about 0.336 V, leaving approximately 23.66 V at the load.

Question 12Electronics Engineering (PRC regulated profession)

In a regulated electronics design, which practice best demonstrates compliance with electromagnetic compatibility requirements at the design stage?

  1. Relying on the enclosure to suppress all emissions
  2. Adding filtering only after EMC test failure
  3. Performing EMC-oriented design review and pre-compliance testing before finalizing the design Correct answer.
  4. Deferring grounding strategy to the installation contractor

Explanation

EMC compliance is most economically achieved by addressing grounding, shielding, and filtering during design review and verifying them with pre-compliance testing. Correcting failures after formal testing is costlier, and enclosure or contractor measures cannot substitute for design-level control.

Question 13Electronics Engineering (PRC regulated profession)

A three-phase 400 V, 50 Hz induction motor nameplate shows a power factor of 0.85. What is the primary reason for installing power-factor correction capacitors at the motor feeder?

  1. To eliminate the need for motor overload protection
  2. To increase the motor's mechanical output torque
  3. To raise the supply frequency to the motor
  4. To reduce the reactive current drawn from the supply and lower line losses Correct answer.

Explanation

Capacitors supply reactive power locally, reducing the reactive current that the supply must deliver and thereby lowering line losses and demand charges. They do not change mechanical output, supply frequency, or the requirement for overload protection.

Question 14Electronics Engineering (PRC regulated profession)

When selecting a circuit breaker for a feeder, which coordination principle ensures that a downstream fault trips only the nearest protective device?

  1. Derating
  2. Cascading
  3. Selective coordination Correct answer.
  4. Neutral grounding

Explanation

Selective coordination sets trip characteristics and time delays so that the device closest to a fault operates first, limiting outage scope. Cascading intentionally uses upstream backup, derating adjusts ratings for conditions, and neutral grounding concerns system earthing.

Question 15Electronics Engineering (PRC regulated profession)

An electronics design includes a safety-related interlock circuit. Which documentation requirement is most important for demonstrating that the interlock achieves its required integrity?

  1. A verbal assurance from the designer at handover
  2. A documented safety analysis with verified integrity level and test evidence Correct answer.
  3. A photograph of the installed panel
  4. A marketing brochure describing the feature

Explanation

Safety-related functions must be supported by a documented analysis showing the achieved integrity level, together with verification and test evidence. Brochures, verbal assurances, and photographs do not provide auditable technical proof of integrity.

Question 16Electronics Engineering (PRC regulated profession)

A PRC design entity subcontracts part of its electronics design work to another entity. Which statement reflects the responsibility rules?

  1. No responsibility applies because the work was subcontracted
  2. The original design entity remains responsible to the client for the whole design Correct answer.
  3. The subcontractor alone is responsible for the subcontracted design quality
  4. Responsibility is automatically transferred to the client

Explanation

The original design entity remains accountable to the client for the entire design, including subcontracted portions, and must ensure the subcontractor is qualified. Subcontracting allocates internal work but does not shift external accountability to the client.

Question 17Electronics Engineering (PRC regulated profession)

A switching power supply exhibits excessive conducted emissions at 150 kHz. Which design measure most directly addresses this low-frequency differential-mode emission?

  1. Adding a larger input differential-mode filter capacitor and inductor Correct answer.
  2. Increasing the switching frequency above 1 MHz
  3. Removing the common-mode choke
  4. Replacing the metal enclosure with plastic

Explanation

Low-frequency conducted emissions in the 150 kHz region are commonly differential-mode, so enlarging the input differential-mode filter elements reduces them. Raising switching frequency shifts energy upward, a plastic enclosure removes shielding, and removing the common-mode choke worsens emissions.

Question 18Electronics Engineering (PRC regulated profession)

A 400 V three-phase feeder supplies a balanced 30 kW load at a power factor of 0.8 lagging. What is the approximate line current?

  1. 75 A
  2. 43 A
  3. 54 A Correct answer.
  4. 65 A

Explanation

Apparent power equals 30 kW divided by 0.8, giving 37.5 kVA. Line current equals apparent power divided by the product of root three and 400 V, approximately 54 A.

Question 19Electronics Engineering (PRC regulated profession)

Which statement best describes the role of a competent supervision entity under PRC construction supervision rules?

  1. It replaces the contractor's quality management system
  2. It monitors and verifies construction quality on behalf of the client Correct answer.
  3. It designs the electrical systems it supervises
  4. It sets the statutory qualification grades for designers

Explanation

A supervision entity acts for the client to monitor and verify that construction conforms to design and standards, without replacing the contractor's own quality system. It does not perform design work or set qualification grades, which are administrative functions.

Question 20Electronics Engineering (PRC regulated profession)

A designer must choose between two cable sizes for a feeder where voltage drop is the limiting criterion. Cable A gives 3 percent drop and cable B gives 5 percent drop; both meet ampacity. Which selection principle applies?

  1. Choose the cable that satisfies the voltage-drop limit with adequate margin Correct answer.
  2. Choose based on lowest purchase price alone
  3. Choose the cable with the highest resistance
  4. Choose the smaller cable because ampacity is satisfied

Explanation

When voltage drop governs, the selected cable must keep drop within the permitted limit, so the option meeting that criterion with margin is correct even if both satisfy ampacity. Price alone or higher resistance would conflict with the governing technical requirement.

Question 21Electronics Engineering (PRC regulated profession)

In a mixed-signal PCB, an analog-to-digital converter shows noise that correlates with digital clock activity. Which layout measure most effectively reduces this coupling?

  1. Separating analog and digital ground returns and joining them at a single reference point Correct answer.
  2. Routing analog and digital return currents through a shared narrow trace
  3. Increasing the digital clock amplitude
  4. Placing the analog input traces parallel to clock lines for a longer distance

Explanation

Separating return paths and joining them at one reference point prevents digital return currents from flowing through analog ground, reducing noise coupling. Shared narrow returns, higher clock amplitude, and long parallel runs all increase coupling.

Question 22Electronics Engineering (PRC regulated profession)

A safety function requires a specified integrity level, and the design team proposes a single-channel architecture with diagnostics achieving only a lower level. What is the correct engineering response?

  1. Remove the diagnostics to simplify the design
  2. Document the gap and proceed to construction
  3. Redesign the architecture to achieve the required integrity level or formally justify a revised requirement Correct answer.
  4. Accept the lower level because diagnostics are present

Explanation

A safety function must meet its specified integrity level, so the architecture must be strengthened or the requirement formally revised through the proper process. Accepting a shortfall, removing diagnostics, or proceeding with a documented gap violates functional safety principles.

Question 23Electronics Engineering (PRC regulated profession)

A 50 Hz transformer feeds a rectifier, and the DC output shows excessive ripple at 100 Hz. Which change most directly reduces this ripple without altering the load?

  1. Removing the filter inductor
  2. Increasing the load current
  3. Reducing the transformer turns ratio
  4. Increasing the filter capacitance Correct answer.

Explanation

Full-wave rectified 50 Hz supply produces ripple at twice the line frequency, and increasing filter capacitance lowers ripple amplitude by holding the DC level between charging pulses. Reducing turns ratio or increasing load current raises ripple, and removing the inductor worsens filtering.

Question 24Electronics Engineering (PRC regulated profession)

During commissioning, measured earth resistance of a substation earthing system exceeds the design limit. Which action is technically correct?

  1. Reduce the test current to obtain a lower reading
  2. Increase the protective device rating to compensate
  3. Commission the system and note the deviation in the report
  4. Improve the earthing system, such as adding electrodes or extending the grid, and retest Correct answer.

Explanation

Earthing resistance above the design limit compromises fault protection and step-touch safety, so the earthing system must be improved and retested until compliant. Recording the deviation, manipulating the test, or altering protection ratings does not correct the underlying deficiency.

Question 25Electronics Engineering (PRC regulated profession)

A design entity is asked to certify that a completed installation matches the approved design. Which document set provides the authoritative basis for this comparison?

  1. The approved design drawings together with approved design changes Correct answer.
  2. The commissioning test plan only
  3. The contractor's internal work schedule
  4. Supplier delivery notes

Explanation

Compliance is judged against the approved design drawings as amended by formally approved design changes, which together define the authorized configuration. Schedules, delivery notes, and test plans support the work but do not define the approved design baseline.

Question 26Electronics Engineering (PRC regulated profession)

A PRC-registered electronics design institute must hold a qualification certificate before it may lawfully sign construction drawings for a new substation automation system. Which authority issues and administers this engineering design qualification?

  1. The project owner's internal quality department
  2. The State Administration for Market Regulation alone
  3. The local fire rescue brigade of the project district
  4. The housing and urban-rural development department of the State Council and its provincial counterparts Correct answer.

Explanation

Engineering design qualifications for construction-related electronics work are administered by the housing and urban-rural development authorities at State Council and provincial levels. The certificate defines the scope and grade of work the entity may legally undertake. Market regulators and fire authorities do not issue design qualification certificates.

Question 27Electronics Engineering (PRC regulated profession)

An electronics design contract specifies a design working life of 25 years for control cabinets installed in an industrial plant. Under PRC construction quality rules, who is responsible for ensuring the design meets this stated working life requirement?

  1. The construction contractor who installs the cabinets
  2. The competent supervision entity
  3. The cabinet manufacturer alone
  4. The design entity that prepared and signed the design documents Correct answer.

Explanation

The design entity is responsible for the technical adequacy of its design, including meeting the specified design working life. Contractors build to the design, and manufacturers supply to specification, but neither owns the design intent. Supervision verifies execution, not design adequacy.

Question 28Electronics Engineering (PRC regulated profession)

In a PRC electronics installation project, the approved design documents must be available on site during construction. Which statement describes the required handling of design document changes after approval?

  1. Any change may be made by the site engineer and recorded in the construction log
  2. Changes are permitted freely provided the contractor agrees
  3. Changes are prohibited once construction starts
  4. Changes affecting safety or function require review and re-approval by the original approving authority Correct answer.

Explanation

Design changes that affect structural safety, major function, or compliance must go back through the original review and approval channel. Routine site adjustments recorded in logs are not a substitute for re-approval of substantive changes. Free changes or outright prohibition both misstate the rule.

Question 29Electronics Engineering (PRC regulated profession)

A low-voltage distribution board in a PRC factory uses a TN-S earthing arrangement. Which conductor function must be kept strictly separate from the neutral conductor throughout the installation?

  1. The control circuit conductor
  2. The switched line conductor
  3. The protective earthing conductor Correct answer.
  4. The line conductor

Explanation

In a TN-S system the protective earthing conductor (PE) and neutral (N) are separate from the source onward and must not be combined downstream. Line and switched conductors carry load current and are unrelated to this separation rule. Control conductors follow their own circuit requirements.

Question 30Electronics Engineering (PRC regulated profession)

An electronics workshop has a 400 V three-phase feeder protected by a 63 A molded case circuit breaker. A new 15 kW resistive heater bank with a power factor of 1.0 is to be added to the feeder. What is the approximate additional line current, and does it fit within spare capacity of 20 A?

  1. About 65 A, so it exceeds the 20 A spare capacity
  2. About 38 A, so it exceeds the 20 A spare capacity
  3. About 22 A, so it exceeds the 20 A spare capacity Correct answer.
  4. About 13 A, so it fits within the 20 A spare capacity

Explanation

Three-phase current is P divided by (sqrt3 times line voltage), giving 15000/(1.732x400) which is about 21.7 A. That exceeds the stated 20 A spare capacity, so the addition cannot simply be connected without re-evaluating the feeder. The other figures come from using single-phase or incorrect voltage assumptions.

Question 31Electronics Engineering (PRC regulated profession)

A design entity proposes to use a new type of surge protective device in a PRC project. Before the device may be applied in the approved design, which requirement is most directly relevant?

  1. The device must carry a foreign certification only
  2. The device must be manufactured in the same province as the project
  3. The device must be the lowest-priced option in its category
  4. The device must be type-tested and certified to the applicable national or industry standard Correct answer.

Explanation

Electrical products used in regulated construction must conform to applicable national or industry standards and be supported by type test or certification evidence. Price, local manufacture, or foreign-only certification do not establish conformity with PRC requirements. Designers should confirm the certificate covers the specific product and rating.

Question 32Electronics Engineering (PRC regulated profession)

A PRC electronics design institute is registered as a Class B entity for a specialty. It is invited to design a system that falls within Class A scope for that specialty. What is the lawful course of action?

  1. Accept the work if the client signs a waiver of qualification requirements
  2. Accept the work and subcontract the whole design to a Class A entity without further arrangement
  3. Accept the work and self-certify the design as equivalent to Class A
  4. Decline unless it partners lawfully with a qualified Class A entity under an approved arrangement Correct answer.

Explanation

An entity may only undertake work within the scope and grade of its qualification. Work beyond that grade requires a lawful arrangement with an appropriately qualified entity rather than a client waiver or self-certification. Simply passing the whole design onward without a proper contractual and responsibility arrangement is not a valid substitute.

Question 33Electronics Engineering (PRC regulated profession)

During design review of a data centre power distribution unit, the reviewer asks for selectivity between the main incoming breaker and a branch breaker. Which arrangement best achieves time-current selectivity?

  1. Reducing the cable size between the two breakers
  2. Using identical breakers with identical settings at both levels
  3. Setting the upstream breaker with a deliberate time delay and higher instantaneous threshold than the downstream device Correct answer.
  4. Increasing the branch breaker rating above the main breaker rating

Explanation

Time-current selectivity is achieved by giving the upstream device a longer delay and higher instantaneous trip threshold so a downstream fault clears locally first. Identical settings tend to trip both devices together, defeating selectivity. Cable size and reversed ratings do not create coordination and may violate protection rules.

Question 34Electronics Engineering (PRC regulated profession)

A PRC design entity signs a contract for an electronics control system and then discovers that the client's functional requirements are incomplete. Which action best reflects proper design-stage quality control?

  1. Proceed to detailed design and resolve gaps during construction
  2. Assume typical values and document them only in the final drawing set
  3. Delegate the clarification to the equipment supplier
  4. Issue a formal request to the client to clarify and confirm the design input before design proceeds Correct answer.

Explanation

Design input must be reviewed and confirmed before design work proceeds, with incomplete or ambiguous requirements formally raised to the client. Proceeding on assumptions shifts risk and can invalidate later approvals. The supplier cannot define the client's functional requirements.

Question 35Electronics Engineering (PRC regulated profession)

An electronics design includes a programmable safety controller for a machine guard interlock. Which document is most important to demonstrate that the achieved integrity meets the required safety function?

  1. The safety requirements specification with verification evidence for the achieved integrity level Correct answer.
  2. The supplier's delivery note
  3. The sales brochure for the controller
  4. The factory acceptance test report for the enclosure paint

Explanation

A safety requirements specification records the required integrity and the verification evidence showing the design achieves it. Brochures, delivery notes, and cosmetic test reports do not establish functional safety performance. The specification links the requirement to the implemented architecture and diagnostics.

Question 36Electronics Engineering (PRC regulated profession)

A design entity is subcontracted to prepare part of an electronics design for a PRC project. Which statement best reflects responsibility for the subcontracted portion?

  1. The subcontractor alone bears responsibility, and the main designer is released from it
  2. Responsibility is shared equally with the competent supervision entity
  3. The main design entity remains responsible for the whole design, including the subcontracted portion Correct answer.
  4. Responsibility passes to the project owner once the subcontract is signed

Explanation

The main design entity retains overall responsibility for the design it signs, including work performed by subcontractors. Subcontracting does not transfer statutory design responsibility to the owner or supervisor. The main entity must control and verify subcontracted output.

Question 37Electronics Engineering (PRC regulated profession)

A switching converter fails radiated emission testing near 30 MHz, and the culprit is identified as a cable acting as an antenna. Which measure most directly reduces the radiated emission?

  1. Adding a common-mode choke and improving cable shielding and return-path layout Correct answer.
  2. Reducing the load current
  3. Increasing the converter switching frequency
  4. Increasing the output capacitor value only

Explanation

Radiated emissions from cables are driven by common-mode currents, so a common-mode choke plus better shielding and return-path control directly reduces them. Raising switching frequency can worsen emissions. Output capacitance and load current changes do not address the antenna mechanism.

Question 38Electronics Engineering (PRC regulated profession)

A 24 V DC solenoid is switched by a relay, and the coil is driven by a transistor. Which measure most effectively protects the transistor from the inductive kick when the solenoid de-energizes?

  1. A higher relay contact rating
  2. A freewheeling diode across the solenoid coil Correct answer.
  3. A capacitor in series with the coil
  4. A larger base resistor

Explanation

An inductive load generates a reverse voltage spike at turn-off, and a freewheeling diode across the coil provides a path that clamps it. A larger base resistor affects drive current, not the spike. Series capacitance blocks DC, and contact rating is unrelated to coil suppression.

Question 39Electronics Engineering (PRC regulated profession)

A PRC project requires an electronics system to be commissioned before acceptance. Which activity best demonstrates that commissioning was properly completed?

  1. A photograph of the completed panel
  2. A signed commissioning record with measured test results compared against design acceptance criteria Correct answer.
  3. An informal email from the equipment supplier
  4. A verbal confirmation from the installation foreman

Explanation

Commissioning evidence should be a formal record with measured values checked against the design acceptance criteria and signed by the responsible parties. Verbal confirmation, photographs, and supplier emails lack the measured comparison needed for acceptance. Records support later verification and handover.

Question 40Electronics Engineering (PRC regulated profession)

A 400 V three-phase feeder supplies a 45 kW balanced load at a power factor of 0.9 lagging. What is the approximate line current?

  1. About 62 A
  2. About 45 A
  3. About 72 A Correct answer.
  4. About 125 A

Explanation

Line current equals P divided by (sqrt3 times line voltage times power factor): 45000/(1.732x400x0.9) which is about 72 A. Ignoring the power factor or using single-phase voltage gives the other figures. The result confirms the importance of including power factor in feeder sizing.

Question 41Electronics Engineering (PRC regulated profession)

An electronics design entity must keep design files, calculation records, and review records for a completed PRC project. Which principle best describes the retention obligation?

  1. Records are the sole responsibility of the contractor
  2. Records must be retained for the period required by law and the contract, and made available for inspection Correct answer.
  3. Records only need to be kept if the client pays a storage fee
  4. Records may be discarded once the project is handed over

Explanation

Design records must be retained for the legally and contractually required period and be available for inspection. Discarding them at handover defeats traceability and statutory audit. Record keeping is a design entity obligation and not contingent on a storage fee.

Question 42Electronics Engineering (PRC regulated profession)

A mixed-signal board shows ADC noise correlated with a digital clock. The analog front end and the digital section currently share a single ground plane with the ADC placed near the clock driver. Which layout change most directly reduces the coupling?

  1. Routing the analog input traces parallel to the clock trace for a longer distance
  2. Moving the ADC away from the clock driver and partitioning analog and digital return currents with a controlled single-point reference Correct answer.
  3. Removing all decoupling capacitors to reduce part count
  4. Increasing the digital clock frequency

Explanation

Separating the sensitive analog front end from the clock source and controlling return-current paths reduces coupling into the ADC. Higher clock frequency or longer parallel runs would worsen coupling. Removing decoupling increases supply noise and is counterproductive.

Question 43Electronics Engineering (PRC regulated profession)

A transformer-rectifier supply shows excessive 100 Hz ripple on its DC output when fed from a 50 Hz supply. Which change most directly reduces the ripple?

  1. Increasing the load current
  2. Increasing the smoothing capacitor value or adding an LC filter stage Correct answer.
  3. Replacing the rectifier diodes with faster types
  4. Reducing the transformer turns ratio

Explanation

Ripple at twice the supply frequency is reduced by increasing smoothing capacitance or adding an LC filter to attenuate the ripple component. Faster diodes address switching speed, not low-frequency ripple. Reducing turns ratio lowers voltage, and higher load current increases ripple.

Question 44Electronics Engineering (PRC regulated profession)

A substation earthing system measures above the design earth resistance limit during commissioning. Which action is most appropriate before acceptance?

  1. Reduce the design limit in the record to match the measurement
  2. Investigate and improve the electrode system, then re-measure against the design limit Correct answer.
  3. Disconnect the earthing system to avoid nuisance trips
  4. Accept the result because earthing resistance is only advisory

Explanation

Measured earthing resistance must meet the design limit, so the electrode system should be improved and re-measured. Altering the limit to match a failing result is falsification. Accepting or disconnecting the earthing system compromises safety and is not permissible.

Question 45Electronics Engineering (PRC regulated profession)

A design entity is asked to confirm that a completed electronics installation matches the approved design. Which document set provides the primary basis for this comparison?

  1. The project meeting minutes
  2. The contractor's purchase orders
  3. The approved design drawings, specifications, and approved change records Correct answer.
  4. The equipment supplier's catalogue

Explanation

Conformity is judged against the approved design drawings, specifications, and any formally approved changes. Purchase orders and catalogues describe procurement, not approved design intent. Meeting minutes may record discussions but do not replace approved documents.

Question 46Electronics Engineering (PRC regulated profession)

A PRC electronics design uses a safety-related circuit where a single fault must not cause loss of the safety function. The proposed architecture is a single channel with no diagnostics. Which assessment is most appropriate?

  1. It is acceptable because single-channel designs are always sufficient
  2. It cannot meet the required integrity without additional redundancy or diagnostic coverage Correct answer.
  3. It is acceptable if the component supplier provides a datasheet
  4. It is acceptable if the installation is supervised

Explanation

A single channel with no diagnostics generally cannot satisfy a requirement that a single fault must not defeat the safety function. Redundancy or diagnostic coverage is needed to detect and respond to faults. Datasheets and supervision do not substitute for architectural measures.

Question 47Electronics Engineering (PRC regulated profession)

A design entity must demonstrate control of its design process for PRC qualification and project audits. Which practice best supports this?

  1. Maintaining controlled procedures, review records, and version-controlled design outputs Correct answer.
  2. Keeping design calculations only in personal notebooks
  3. Relying on verbal handovers between engineers
  4. Storing all records on a single unbacked personal computer

Explanation

A controlled design process relies on documented procedures, formal reviews, and version-controlled outputs that can be audited. Personal notebooks, verbal handovers, and unbacked single devices do not provide traceable control. These records also support design change management.

Question 48Electronics Engineering (PRC regulated profession)

A 400 V three-phase motor circuit has a full-load current of 40 A. The designer selects a contactor and overload relay. Which overload relay setting best protects the motor while allowing normal starting?

  1. Set at zero to ensure immediate trip
  2. Set at the motor full-load current with a trip class appropriate to the starting duty Correct answer.
  3. Set at twice the full-load current to avoid nuisance trips
  4. Set at the upstream breaker rating

Explanation

Overload protection is set at the motor full-load current, with a trip class matched to the starting duty so normal starts do not cause nuisance tripping. Setting at twice full load or at the breaker rating leaves the motor unprotected. A zero setting prevents normal operation.

Question 49Electronics Engineering (PRC regulated profession)

An electronics design includes a 24 V DC field wiring loop that runs 200 m through an industrial plant alongside variable-frequency drive cables. Which measure most directly reduces induced noise on the loop?

  1. Using twisted-pair signal wiring with shielded cable and separating it from the drive cables Correct answer.
  2. Removing the shield to reduce capacitance
  3. Increasing the loop supply voltage to 48 V
  4. Routing the loop parallel and close to the drive cables for a shorter run

Explanation

Twisted pairs with shielding and physical separation from noisy drive cables reduce magnetically and capacitively induced noise. Raising voltage does not remove the coupling mechanism. Removing the shield or running closer to the drives increases noise pickup.

Question 50Electronics Engineering (PRC regulated profession)

A PRC project requires review of an electronics design before construction. Which statement best describes the purpose of the statutory design document review?

  1. To negotiate the contract price
  2. To replace the design entity's internal quality checks
  3. To select the construction contractor
  4. To confirm the design meets mandatory public interest, safety, and standard requirements before construction Correct answer.

Explanation

Statutory design review checks compliance with mandatory requirements concerning public interest, safety, and applicable standards before construction begins. It does not set contract prices or select contractors. It complements but does not replace the designer's internal quality control.