FREE Journeyman Electrician’s Basic Formula Questions and Answers

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What is the highest value that the power factor can possibly be?

Correct! Wrong!

The power factor (PF) is the proportion of real power, measured in watts, kilowatts, or kW, to perceived power, measured in volt-amps, VA, or kVA. A decimal or a percentage that doesn't go over 100% is used to express power factor.

Calculate the power factor of a 5 kW load using a 208 volt, single phase source to draw 30 amperes of current.

Correct! Wrong!

• Power Factor formula: PF = (P(kW) x 1,000) / (E x I)
In this case: PF = (5 kW x 1,000) / (208 volts x 30 amps)
= 5,000 watts / 6,240 VA
=0.80 80%

Given that the electrical load has a power factor of 0.8 and a voltage of 240 volts, determine its current.

Correct! Wrong!

When the voltage and power factor are known, the formula used to calculate the current of a single-phase electrical load or system is:
• I = Watts / ( Volts x PF ) Plugging in the given values of watts, volts and PF, we have
• I = 300 / (240 xx 0.8) = 1.56 amps

Find the voltage drop of two copper wires of size 10 AWG that are 100 feet away from the voltage source and are powering an 8-amp load. Given: The two conductors' combined resistance is 0.2 ohms.

Correct! Wrong!

When the current and resistance in an electrical circuit are known, the formula used to calculate the voltage or voltage drop is:
• E = I x R
In this case, •E = 8 amps x 0.2 ohms = 1.6 volts

Six horsepower equals:

Correct! Wrong!

746 watts make up one horsepower. Six horsepower is therefore equal to 6 × 746 watts, or 4,476 watts.

Except when the wiring is feeding the related pool equipment, underground wiring is not allowed under a permanently installed swimming pool or within ____ of the pool.

Correct! Wrong!

Except when the wiring is feeding the related pool equipment, underground wiring is not allowed under a permanently installed swimming pool or within 5 feet of the pool. This requirement helps ensure the safety and proper functioning of electrical installations in the vicinity of swimming pools, preventing potential hazards and damage to the wiring. Always follow local electrical codes and regulations when installing wiring near swimming pools.

The power supply for household appliances with surface heating components that have a MAXIMUM demand of more than ____ must be split into two (2) or more circuits.

Correct! Wrong!

The power supply for household appliances with surface heating components that have a maximum demand of more than 60 amperes must be split into two (2) or more circuits. This requirement is to ensure that the electrical load is distributed properly and that the circuits can handle the higher current demands of such appliances, reducing the risk of overloading a single circuit.

Class 3 single conductors are not permitted to be any smaller than .

Correct! Wrong!

Class 3 single conductors are not permitted to be any smaller than 18 AWG. This requirement ensures that the conductors have sufficient size to carry the intended currents safely and reliably, particularly in low-voltage signaling and communication systems.

How many amperes of current, in terms of watts, can a microwave oven rated at 1,200 watts draw?

Correct! Wrong!

• Current formula: I = P/E
• In this case: 1 = 1,200 watts / 120 volts = 10 amperes

What does the letter "E" stand for in the PIE formula circle?

Correct! Wrong!

P= I x E should be circled in the PIE formula. Power, current intensity, and voltage are all represented by the letters "P," "I," and "E," respectively.

When protected by a 15-ampere circuit breaker, a branch circuit supplied by size 12 AWG conductors is a ____ rated branch circuit.

Correct! Wrong!

When protected by a 15-ampere circuit breaker, a branch circuit supplied by size 12 AWG conductors is a 15-ampere rated branch circuit. The size of the circuit conductors and the rating of the circuit breaker should match to ensure safe operation and prevent overloading of the wiring.

When will the voltage and the current both peak and reach zero simultaneously?

Correct! Wrong!

The peak and zero points of the voltage and the current will occur simultaneously when they are "in-phase." We refer to this as unity or a power factor of 100 percent.

What is the MINIMUM size copper grounding electrode conductor needed when linked to the concrete-encased reinforcing building steel in a situation where an ac electrical service is supplied using four (4) parallel sets of size 500 kcmil aluminum ungrounded conductors?

Correct! Wrong!

The minimum size copper grounding electrode conductor needed when linked to the concrete-encased reinforcing building steel and supplying an AC electrical service using four (4) parallel sets of size 500 kcmil aluminum ungrounded conductors is typically 3/0 AWG. This conductor size is determined based on various factors, including the size of the service conductors and the grounding requirements outlined in the National Electrical Code (NEC) or applicable local electrical codes. Always verify the specific requirements of the code you're following for accurate sizing.

When a 480 Y/277 volt, three-phase, 4-wire electrical system is used to supply a commercial service with a 400 ampere rating, the service is rated as follows:

Correct! Wrong!

• Power Formula, 3-phase: P(kVA) = (1 x E x 1.732) / 1,000
In this case:
P = (400A x 480V x 1.732) / 1,000
= 332,544 VA / 1,000
= 332.5 kVA

If a 1/2 in. conduit seal is required for a trade size 1/2 in. rigid metal conduit (RMC) installed in a Class I location, the sealing compound's minimum thickness must not be less than ?

Correct! Wrong!

If a 1/2 in. conduit seal is required for a trade size 1/2 in. rigid metal conduit (RMC) installed in a Class I location, the sealing compound's minimum thickness must not be less than 5/8 in. This is to ensure effective sealing and protection against the passage of gases, vapors, or flames in hazardous locations.

The current in a single-phase circuit is defined by which formula?

Correct! Wrong!

The following equation can be used to calculate how much power is available for a single-phase circuit, load, or electrical system:
• P = I x E
Consequently, the following is the proper formula for defining the current in a single-phase circuit:
• I = P/E

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