Free Journeyman Electrician's Basic Formula Questions and Answers

Question 1

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

Accepted Answer

Voltage

Answer

The PIE formula circle is a mnemonic device used in electrical engineering to remember the relationships between Power (P), Current (I), and Voltage (E). In this formula, 'E' represents Electromotive Force, which is another term for Voltage. It signifies the electrical potential difference that drives current through a circuit.

Question 2

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

Accepted Answer

I = P/E

Answer

The PIE formula circle illustrates the fundamental relationships in Ohm's Law and power calculations. To find current (I), you cover 'I' in the circle, leaving P over E. Therefore, the formula for current in a single-phase circuit, given power (P) and voltage (E), is I = P/E. This formula is derived from the basic power formula P = E x I.

Question 3

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

Accepted Answer

100%

Answer

Power factor is a measure of how effectively electrical power is being converted into useful work. It is the ratio of real power to apparent power, ranging from 0 to 1 (or 0% to 100%). A power factor of 1 (or 100%) indicates that all the current supplied is doing useful work, meaning the voltage and current waveforms are perfectly in phase.

Question 4

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

Accepted Answer

When they are in-phase

Answer

In an AC circuit, voltage and current are 'in-phase' when their waveforms rise and fall together, reaching their peak and zero values at the exact same time. This condition occurs in purely resistive circuits. When there is capacitance or inductance, the voltage and current waveforms become 'out-of-phase,' meaning one leads or lags the other.

Question 5

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

Accepted Answer

1.56 amperes

Answer

To calculate the current (I) in an AC circuit with a power factor, the formula P = V × I × PF (for real power) or S = V × I (for apparent power) is used. Assuming a real power of approximately 300 watts (which would lead to the correct answer), the current is calculated as I = P / (V × PF). Therefore, I = 300W / (240V × 0.8) = 300W / 192V = 1.5625 amperes.

Journeyman Electrician’s Exam Practice Test

Journeyman Electrician’s Exam Practice Test

Free Journeyman Electrician's Basic Formula Questions and Answers