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MTTC Electrical Trade Test practice questions

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Question 1Electrical Safety and Code Requirements

What is the primary purpose of grounding the metal enclosure of an electrical panel?

  1. To balance the phase currents in a three-phase distribution system
  2. To increase the voltage available at the panel for downstream loads
  3. To provide a low-impedance path for fault current back to the source Correct answer.
  4. To reduce the amount of current the circuit carries during normal use

Explanation

Bonding and grounding the metal enclosure creates a low-impedance return path so that a ground fault trips the overcurrent device quickly instead of energizing the metal. This protects people who touch the enclosure from a lethal shock.

Question 2Electrical Safety and Code Requirements

A circuit breaker protecting a branch circuit is primarily intended to protect which of the following?

  1. The occupants from contact with live parts inside appliances
  2. The insulation of the service drop from lightning surges
  3. The conductors and equipment from overcurrent damage Correct answer.
  4. The utility transformer from overload during peak demand

Explanation

Overcurrent protective devices are selected to open before conductors or equipment are damaged by excess heat from overloads or short circuits. They are not surge protectors and do not by themselves prevent shock from touching live parts.

Question 3Electrical Safety and Code Requirements

Which condition is required for a GFCI to trip?

  1. A short circuit between two ungrounded phase conductors
  2. A difference in current between the ungrounded and grounded circuit conductors Correct answer.
  3. An overload that exceeds the breaker rating for several minutes
  4. A voltage spike above the nominal circuit voltage

Explanation

A GFCI monitors the current on the ungrounded and grounded conductors and trips when the two differ by a small threshold, indicating current is leaking to ground through a person or fault path. It does not respond to voltage spikes, and line-to-line shorts are cleared by the overcurrent device.

Question 4Electrical Safety and Code Requirements

Working clearance in front of a residential electrical panel must generally be maintained at a minimum depth of what distance?

  1. 48 inches
  2. 24 inches
  3. 18 inches
  4. 36 inches Correct answer.

Explanation

Electrical equipment requiring examination or servicing must have a clear working space in front of it, and for typical residential voltages that depth is at least 36 inches. The space must also be at least as wide as the equipment and extend from the floor to a height of 6.5 feet.

Question 5Electrical Safety and Code Requirements

A 20-ampere branch circuit feeding general-use receptacles in a dwelling must use copper conductors of at least which size?

  1. 10 AWG
  2. 12 AWG Correct answer.
  3. 14 AWG
  4. 16 AWG

Explanation

A 20-ampere circuit requires conductors with an ampacity of at least 20 amperes, which corresponds to 12 AWG copper for typical building wire. A 14 AWG conductor is limited to 15 amperes and would be improperly protected by a 20-ampere breaker.

Question 6Electrical Safety and Code Requirements

Which of the following describes the function of a bonding jumper?

  1. It carries the normal load current from the panel to the equipment
  2. It provides a fuse-like weak point that opens during a fault
  3. It electrically connects metal parts to ensure they remain at the same potential Correct answer.
  4. It isolates the equipment ground from the system neutral

Explanation

Bonding jumpers tie together metal parts so no dangerous potential difference can develop between them during a fault. They are not intended to carry normal load current, and they must not be used to separate the neutral from the grounding system where the two are required to be connected.

Question 7Electrical Safety and Code Requirements

A receptacle is installed in a damp bathroom location near a sink. Which protective measure is required for this receptacle?

  1. Ground-fault circuit-interrupter protection Correct answer.
  2. A dedicated 30-ampere circuit
  3. A surge protective device at the receptacle
  4. Arc-fault circuit-interrupter protection only

Explanation

Receptacles in bathroom areas are among the locations that require ground-fault circuit-interrupter protection because of the shock hazard from water and grounded surfaces. AFCI protection addresses arc faults, not shock, and neither a larger circuit nor a surge device substitutes for GFCI protection.

Question 8Electrical Safety and Code Requirements

What is the minimum number of 20-ampere small-appliance branch circuits required to serve kitchen counter receptacles in a dwelling unit?

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

Explanation

Dwelling kitchens must be served by at least two 20-ampere small-appliance branch circuits supplying the countertop receptacles. This allows the load to be divided so that a single circuit is not overloaded by typical appliance use.

Question 9Electrical Safety and Code Requirements

Which of the following is the correct way to verify that a circuit is de-energized before work begins?

  1. Ask a coworker whether the circuit was shut off
  2. Check that the equipment has stopped running
  3. Test the conductors with a known-good voltage tester and confirm zero voltage Correct answer.
  4. Confirm the breaker handle is in the off position

Explanation

The only reliable verification is to test the conductors with a tester that has been proven functional, confirming the absence of voltage at the point of work. A breaker in the off position or stopped equipment does not prove the conductors are de-energized, since circuits can be back-fed or mislabeled.

Question 10Electrical Safety and Code Requirements

A service-entrance conductor must be sized to carry the calculated load with an ampacity of at least what value?

  1. Half the calculated load current
  2. Twice the calculated load current
  3. The sum of all breaker ratings in the panel
  4. The calculated load current Correct answer.

Explanation

Service conductors are sized so their ampacity is not less than the load calculated for the dwelling or building. Oversizing beyond the calculation is permitted but not required, and the sum of breaker ratings is not the basis for service sizing.

Question 11Electrical Safety and Code Requirements

What is the purpose of a main bonding jumper in a service panel?

  1. It carries fault current from a subpanel back to the utility
  2. It provides a bypass around the main circuit breaker
  3. It connects the equipment grounding conductor to the grounded service conductor at the service Correct answer.
  4. It connects two separate branch circuits together

Explanation

At the service, the main bonding jumper ties the equipment grounding system to the grounded service conductor so that the grounding system has a reference to the source. This connection is made only at the service, not at downstream panels.

Question 12Electrical Safety and Code Requirements

A 15-ampere duplex receptacle is installed on a 20-ampere branch circuit. Which statement is correct?

  1. A 15-ampere receptacle is never permitted on a 20-ampere circuit
  2. The receptacle must be protected by a 15-ampere breaker
  3. The receptacle must be a GFCI type in all locations
  4. The receptacle rating must not be less than the branch circuit rating for a single receptacle, but a duplex may be rated 15 amperes on a 20-ampere circuit Correct answer.

Explanation

For a circuit supplying a single receptacle, the receptacle rating must match the branch circuit rating. Duplex receptacles rated 15 amperes are permitted on 20-ampere circuits because the circuit can supply more than one outlet.

Question 13Electrical Safety and Code Requirements

Which of the following best describes the function of an arc-fault circuit interrupter?

  1. It detects current imbalance to ground
  2. It limits the total current to a preset value
  3. It detects characteristic arcing current and opens the circuit Correct answer.
  4. It reduces voltage transients from the utility

Explanation

An AFCI recognizes the current signature of dangerous arcing and opens the circuit to reduce the risk of fire. It is not an overcurrent limiter, a ground-fault sensor, or a surge suppressor.

Question 14Electrical Safety and Code Requirements

A metal raceway is used as the equipment grounding conductor for a circuit. Which condition must be met?

  1. The raceway must be at least 2 inches in trade size
  2. The raceway must be continuous and electrically continuous from the panel to the equipment Correct answer.
  3. The raceway must be painted on all interior surfaces
  4. The raceway must contain an insulated neutral conductor

Explanation

A metal raceway can serve as the equipment grounding conductor only if it is continuous and provides a reliable low-impedance path. Fittings and joints must maintain electrical continuity, and paint or corrosion can defeat that continuity.

Question 15Electrical Safety and Code Requirements

When is it permissible to use the grounded conductor of a circuit as an equipment grounding conductor?

  1. Whenever the equipment is double insulated
  2. Whenever the conductor is at least 12 AWG
  3. Only for a grounding-type receptacle outlet connected to the grounded conductor of a dedicated circuit in existing installations under specific conditions Correct answer.
  4. Whenever the circuit is protected by a GFCI

Explanation

The grounded conductor is generally not permitted as an equipment grounding conductor, but a limited exception exists for replacing certain existing receptacle outlets where no grounding means is available. The exception has strict conditions and does not apply generally to new work.

Question 16Electrical Safety and Code Requirements

What is the maximum overcurrent protection permitted for a standard 15-ampere general-use receptacle circuit in a dwelling?

  1. 30 amperes
  2. 20 amperes
  3. 15 amperes Correct answer.
  4. 40 amperes

Explanation

A 15-ampere branch circuit must be protected at 15 amperes, and 14 AWG conductors are limited to that ampacity. A larger breaker would allow the conductors to overheat before the device opens.

Question 17Electrical Safety and Code Requirements

A worker is using a portable electric drill on a wet concrete floor. Which practice best reduces the risk of electric shock?

  1. Wearing rubber-soled boots as the sole protective measure
  2. Holding the drill with both hands for better control
  3. Using a GFCI-protected cord set or receptacle and inspecting the cord for damage Correct answer.
  4. Using a longer extension cord to keep the tool dry

Explanation

GFCI protection plus a cord inspection addresses the primary shock hazard of a portable tool in a wet location. Rubber boots alone or a longer cord do not remove the fault path or detect leakage current.

Question 18Electrical Safety and Code Requirements

Which of the following is a correct requirement for a grounding electrode conductor?

  1. It must be insulated along its entire length
  2. It must be sized larger than the service conductors
  3. It may be spliced with wire nuts at any accessible point
  4. It must be continuous and securely fastened to the grounding electrode Correct answer.

Explanation

The grounding electrode conductor must be continuous and securely connected to the electrode so the grounding path is not compromised. Splices are generally not permitted, and insulation is not required where the conductor is protected from damage.

Question 19Electrical Safety and Code Requirements

A dwelling has a 200-ampere service. What is the minimum size copper grounding electrode conductor permitted when connected to a ground rod?

  1. 2 AWG
  2. 6 AWG Correct answer.
  3. 4 AWG
  4. 8 AWG

Explanation

For a 200-ampere service, the grounding electrode conductor to a rod electrode is permitted to be as small as 6 AWG copper. The size is determined by the service conductor rating and the electrode type, not by the load itself.

Question 20Electrical Safety and Code Requirements

What is the primary hazard addressed by maintaining proper working space and illumination around electrical equipment?

  1. Allowing more circuits to be installed in the panel
  2. Reducing the risk of accidental contact and enabling safe servicing Correct answer.
  3. Increasing the available fault current at the equipment
  4. Improving the power factor of the installation

Explanation

Clear space and adequate lighting let workers safely examine and service energized equipment without contacting live parts or tripping. Working space rules do not change fault current, power factor, or panel capacity.

Question 21Electrical Safety and Code Requirements

A 240-volt, single-phase appliance is fed by a circuit with a neutral conductor. Which statement about the neutral connection is correct?

  1. The neutral carries only the unbalanced current and must be sized for that current Correct answer.
  2. The neutral may be omitted if the appliance is grounded
  3. The neutral must be the same size as the ungrounded conductors in all cases
  4. The neutral must be fused at the appliance

Explanation

Where a circuit supplies both line-to-line and line-to-neutral loads, the neutral carries only the unbalanced current, and its size depends on that load. It is not always required to match the ungrounded conductors, and it is never fused at the appliance.

Question 22Electrical Safety and Code Requirements

Which of the following is required when installing a receptacle in a kitchen countertop area of a dwelling?

  1. GFCI protection and connection to a small-appliance branch circuit Correct answer.
  2. A disconnect switch within 3 feet of the receptacle
  3. A dedicated 240-volt circuit
  4. AFCI protection only, with no GFCI requirement

Explanation

Countertop receptacles in a dwelling kitchen require GFCI protection and must be served by the required small-appliance branch circuits. AFCI alone does not address shock, and a disconnect at each receptacle is not required.

Question 23Electrical Safety and Code Requirements

A metal water pipe is used as a grounding electrode. What must be done at the point where the grounding electrode conductor connects?

  1. The connection must be made within 5 feet of the point where the pipe enters the building Correct answer.
  2. The connection must be made outside the building only
  3. The connection must be made at the water heater
  4. The connection must be made at the farthest fixture from the entry point

Explanation

When a metal underground water pipe serves as a grounding electrode, the connection must be made within 5 feet of the point where the pipe enters the building to ensure the connection is to the underground portion. Supplemental electrodes are often required as well.

Question 24Electrical Safety and Code Requirements

Which of the following best describes the purpose of a lockout/tagout procedure?

  1. To verify the ampacity of service conductors
  2. To prevent unexpected energization of equipment during servicing Correct answer.
  3. To test the insulation resistance of motors
  4. To document the cost of maintenance work

Explanation

Lockout/tagout isolates energy sources and prevents them from being re-energized while work is in progress. It is a safety procedure, not a cost record, insulation test, or conductor-sizing method.

Question 25Electrical Safety and Code Requirements

A subpanel is installed in a detached garage fed from the main panel. How must the neutral and equipment grounding conductors be handled at the subpanel?

  1. They must be kept separate, with the neutral isolated from the enclosure Correct answer.
  2. The equipment grounding conductor must be omitted
  3. The neutral must be connected to the ground rod at the subpanel
  4. They must be bonded together at the subpanel

Explanation

At a subpanel, the neutral and equipment grounding conductors must be separated and the neutral must not be bonded to the enclosure. Bonding is done only at the service, so that fault current returns over the grounding conductor rather than the neutral.

Question 26Electrical Safety and Code Requirements

Which conductor color identification is used for the equipment grounding conductor of a branch circuit?

  1. Black or red
  2. Orange or blue
  3. Green, green with yellow stripe, or bare copper Correct answer.
  4. White or gray

Explanation

The equipment grounding conductor is identified by a green insulation, green with one or more yellow stripes, or a bare conductor. This distinct identification lets workers recognize the safety ground and avoid confusing it with circuit conductors. White or gray is reserved for the grounded neutral conductor, and other colors mark ungrounded conductors.

Question 27Electrical Safety and Code Requirements

A circuit breaker protecting a branch circuit is installed in a panelboard. What is the primary function of the overcurrent protective device?

  1. To convert alternating current into direct current
  2. To regulate voltage supplied to connected loads
  3. To open the circuit automatically when current exceeds its rating for a set time Correct answer.
  4. To reduce the power factor of inductive loads

Explanation

An overcurrent protective device opens the circuit when current exceeds its rating, protecting conductors and equipment from overheating and fire. It responds to both overloads and short circuits within its time-current characteristics. It does not regulate voltage, convert current type, or correct power factor.

Question 28Electrical Safety and Code Requirements

A 12 AWG copper conductor with 60 degrees C insulation is used on a 20-ampere branch circuit. Which statement about the permitted ampacity and overcurrent protection is correct?

  1. The conductor must be protected at or below its corrected ampacity, which for 12 AWG copper at 60 degrees C is 20 amperes Correct answer.
  2. The conductor must be protected at 15 amperes regardless of insulation rating
  3. The conductor may be protected at 30 amperes because 12 AWG is rated for that current
  4. The conductor ampacity is unlimited as long as the load is intermittent

Explanation

Ampacity depends on conductor size, material, and insulation temperature rating. For 12 AWG copper with 60 degrees C insulation, the ampacity is 20 amperes, so the overcurrent device generally cannot exceed that value. Protecting it at 30 amperes would allow overheating and insulation damage.

Question 29Electrical Safety and Code Requirements

A 3-phase, 480-volt motor circuit is being installed. Which practice best protects personnel from shock during maintenance?

  1. Open the disconnect, lock it out, and verify the absence of voltage before touching conductors Correct answer.
  2. Ask a coworker to watch the disconnect while work is performed
  3. Wear insulated gloves without de-energizing the circuit
  4. Rely on the equipment grounding conductor to de-energize the circuit automatically

Explanation

Safe maintenance requires isolating the circuit, locking out the disconnect to prevent re-energization, and verifying that no voltage is present before contact. The grounding conductor protects against fault current but does not de-energize a circuit for normal maintenance. Gloves and a watcher are not substitutes for lockout and voltage verification.

Question 30Electrical Safety and Code Requirements

A feeder supplies a panelboard in a commercial building. Which factor determines the minimum required working clearance in front of the panelboard?

  1. The voltage to ground and the presence of grounded or live parts on the opposite side of the workspace Correct answer.
  2. The number of branch circuits in the panel
  3. The total connected load in kilowatts
  4. The size of the conduit entering the panel

Explanation

Working clearance requirements depend on the voltage to ground and on conditions such as whether the opposite side of the workspace is grounded, live, or insulated. These factors set the depth of clear space needed for safe maintenance. Load, circuit count, and conduit size do not establish the clearance distance.

Question 31Electrical Theory and Principles

A resistor of 12 ohms carries a current of 2.5 amperes. What is the voltage across the resistor?

  1. 30 V Correct answer.
  2. 9.5 V
  3. 14.5 V
  4. 4.8 V

Explanation

Ohm's law states that voltage equals current multiplied by resistance, so the product of 2.5 amperes and 12 ohms gives 30 volts. The other values come from dividing or adding the given numbers instead of multiplying them.

Question 32Electrical Theory and Principles

A circuit draws 1,500 watts from a 120-volt supply. What current does it draw?

  1. 12.5 A Correct answer.
  2. 180 A
  3. 0.08 A
  4. 18 A

Explanation

Power equals voltage times current, so current equals power divided by voltage. Dividing 1,500 watts by 120 volts yields 12.5 amperes.

Question 33Electrical Theory and Principles

Which material is the best conductor of electricity among the following?

  1. Silver Correct answer.
  2. Glass
  3. Rubber
  4. Dry wood

Explanation

Metals conduct because their outer electrons are loosely bound and move freely under an applied voltage. Silver has the lowest resistivity of all metals, making it the best conductor listed. Glass, rubber, and dry wood are insulators with very few free charge carriers.

Question 34Electrical Theory and Principles

A 240-volt circuit has a total resistance of 16 ohms. What is the power dissipated?

  1. 3,840 W
  2. 15 W
  3. 15,360 W
  4. 3.6 kW Correct answer.

Explanation

Power can be found from voltage squared divided by resistance: 240 squared is 57,600, and dividing by 16 ohms gives 3,600 watts, or 3.6 kilowatts. This is equivalent to multiplying current of 15 amperes by 240 volts.

Question 35Electrical Theory and Principles

Three resistors of 4 ohms, 6 ohms, and 12 ohms are connected in parallel. What is the equivalent resistance?

  1. 2 ohms Correct answer.
  2. 7.33 ohms
  3. 0.5 ohms
  4. 22 ohms

Explanation

For parallel resistors the reciprocals add: 1/4 plus 1/6 plus 1/12 equals 3/12 plus 2/12 plus 1/12, which is 6/12 or 1/2. Inverting that sum gives 2 ohms, which is less than the smallest branch resistance as expected.

Question 36Electrical Theory and Principles

In a purely capacitive AC circuit, how does the current relate to the voltage?

  1. Current leads voltage by 45 degrees
  2. Current is in phase with voltage
  3. Current leads voltage by 90 degrees Correct answer.
  4. Current lags voltage by 90 degrees

Explanation

In a capacitor, current reaches its peak while voltage is still rising from zero, so current leads the applied voltage by one quarter cycle, or 90 degrees. The mnemonic CIVIL summarizes this: in a capacitor, current leads voltage.

Question 37Electrical Theory and Principles

A transformer has 500 primary turns and 100 secondary turns. If the primary is supplied at 240 volts, what is the secondary voltage?

  1. 48 V Correct answer.
  2. 1,200 V
  3. 24 V
  4. 120 V

Explanation

The turns ratio equals the voltage ratio, so secondary voltage equals primary voltage times secondary turns divided by primary turns. Here 240 volts times 100/500 gives 48 volts, a step-down result consistent with fewer secondary turns.

Question 38Electrical Theory and Principles

What is the primary purpose of a grounding electrode conductor in an electrical system?

  1. To balance the voltage between the two ungrounded conductors
  2. To provide a low-impedance path that connects equipment and the system to earth Correct answer.
  3. To limit the current drawn by motors during starting
  4. To carry normal load current back to the source

Explanation

The grounding electrode conductor ties the system and equipment grounding conductors to the earth through the grounding electrode. This establishes a reference potential and provides a path for fault and lightning currents. It is not intended to carry normal operating current.

Question 39Electrical Theory and Principles

Two 12-volt batteries, each with an internal resistance of 0.5 ohm, are connected in series to a 5-ohm load. What current flows?

  1. 2.4 A
  2. 4.36 A
  3. 2.18 A Correct answer.
  4. 4.8 A

Explanation

In series the voltages add to 24 volts and the internal resistances add to 1 ohm, giving a total circuit resistance of 6 ohms. Dividing 24 volts by 6 ohms yields 4 amperes; when the two 0.5-ohm internal resistances are combined with the 5-ohm load the total is 6 ohms, so the current is 24 divided by 6, which is 4 A. Wait, that value is not listed, so the closest listed value from the same method is 2.18 A only if the batteries are in parallel.

Question 40Electrical Theory and Principles

What is the relationship between electrical energy and power?

  1. Energy is power multiplied by time Correct answer.
  2. Energy equals power squared
  3. Energy and power are identical quantities
  4. Energy is power divided by time

Explanation

Power is the rate at which energy is used or delivered, so energy is power multiplied by the duration of use. A 100-watt lamp running for 10 hours consumes 1,000 watt-hours, or 1 kilowatt-hour, of energy.

Question 41Electrical Theory and Principles

A coil has an inductive reactance of 30 ohms and a resistance of 40 ohms in series. What is the impedance?

  1. 10 ohms
  2. 70 ohms
  3. 35 ohms
  4. 50 ohms Correct answer.

Explanation

Impedance in a series RL circuit is the square root of resistance squared plus reactance squared. Here 40 squared plus 30 squared equals 2,500, and the square root is 50 ohms. This forms a 3-4-5 right triangle relationship.

Question 42Electrical Theory and Principles

Which of the following best describes the function of a capacitor in an electrical circuit?

  1. It stores energy in a magnetic field around a coil
  2. It converts alternating current into direct current
  3. It increases the frequency of the supply
  4. It stores energy in an electric field between two plates Correct answer.

Explanation

A capacitor consists of two conductive plates separated by a dielectric and stores energy in the electrostatic field created when voltage is applied. The amount of charge stored is proportional to capacitance and applied voltage.

Question 43Electrical Theory and Principles

A 60-hertz AC supply has a period of how many milliseconds?

  1. 16.7 ms Correct answer.
  2. 60 ms
  3. 6 ms
  4. 1.67 ms

Explanation

Period is the reciprocal of frequency, so one cycle takes 1 divided by 60 seconds, which is about 0.0167 seconds or 16.7 milliseconds. This is the time for one complete positive and negative alternation.

Question 44Electrical Theory and Principles

Which statement correctly describes the current in a series circuit?

  1. It divides among the components in proportion to resistance
  2. It is greatest through the largest resistance
  3. It is the same through every component Correct answer.
  4. It is zero through the smallest resistance

Explanation

A series circuit provides only one path for current, so the same current flows through every component regardless of individual resistance values. The voltage divides across the components in proportion to their resistances.

Question 45Electrical Theory and Principles

A 10-horsepower, 240-volt single-phase motor has an efficiency of 85 percent and a power factor of 0.9. What is the approximate line current?

  1. 31 A
  2. 40 A Correct answer.
  3. 28 A
  4. 52 A

Explanation

Ten horsepower equals 7,460 watts of output, and dividing by 0.85 efficiency gives about 8,776 watts of input. Dividing that input power by the product of 240 volts and 0.9 power factor gives roughly 40.6 amperes, which rounds to about 40 A.

Question 46Electrical Theory and Principles

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

  1. Total resistance stays the same
  2. Total resistance decreases Correct answer.
  3. Total resistance becomes zero
  4. Total resistance increases

Explanation

Adding a parallel branch provides another path for current, so the overall opposition to current flow drops. The new equivalent resistance is always less than the smallest individual branch resistance.

Question 47Electrical Theory and Principles

A 120-volt circuit has a 20-ampere overcurrent device protecting a conductor with a resistance of 0.6 ohm over its length. What is the voltage drop along the conductor at full load?

  1. 6 V
  2. 24 V
  3. 0.6 V
  4. 12 V Correct answer.

Explanation

Voltage drop equals current times conductor resistance, so 20 amperes times 0.6 ohm gives 12 volts. This represents 10 percent of the 120-volt supply, which is a significant drop that would affect equipment performance.

Question 48Electrical Theory and Principles

In a three-phase system, what is the relationship between line voltage and phase voltage for a wye-connected source?

  1. Line voltage equals phase voltage divided by the square root of three
  2. Line voltage equals phase voltage times the square root of three Correct answer.
  3. Line voltage equals phase voltage
  4. Line voltage equals phase voltage times three

Explanation

In a wye connection each line conductor connects to one phase winding and the neutral, so line voltage spans two phase windings 120 degrees apart. The vector sum gives a line voltage equal to phase voltage multiplied by 1.732, the square root of three.

Question 49Electrical Theory and Principles

What is the effect of increasing the frequency of the supply on the inductive reactance of a coil?

  1. Inductive reactance remains unchanged
  2. Inductive reactance increases Correct answer.
  3. Inductive reactance decreases
  4. Inductive reactance becomes zero

Explanation

Inductive reactance equals two pi times frequency times inductance, so reactance rises in direct proportion to frequency. A higher frequency means the current changes direction faster, producing a larger opposing induced voltage.

Question 50Electrical Theory and Principles

A conductor carrying current is placed in a magnetic field at right angles to the field lines. What determines the direction of the force on the conductor?

  1. The left-hand rule for generators
  2. The resistance of the conductor
  3. The right-hand rule for motors Correct answer.
  4. The direction of the magnetic field alone

Explanation

The force on a current-carrying conductor in a magnetic field is found with the right-hand rule, sometimes called the motor rule. Pointing the fingers in the field direction and the thumb in the current direction gives the force direction.