Licensed Electrical Contractor Electrical Theory & Fundamentals 3

Question 1

What is the formula for calculating electrical power in a DC circuit?

Accepted Answer

P = V × I

Answer

Electrical power (watts) equals voltage (volts) multiplied by current (amperes): P = V × I.

Question 2

What is the phase relationship between voltage and current in a purely inductive circuit?

Accepted Answer

Current lags voltage by 90°

Answer

In a purely inductive circuit, current lags voltage by 90° because the inductor opposes changes in current.

Question 3

What is the term for the total opposition to current flow in an AC circuit, combining resistance and reactance?

Accepted Answer

Impedance

Answer

Impedance (Z) is the total opposition to AC current flow, combining resistance (R) and reactance (X), expressed in ohms.

Question 4

A 120V source is connected to a 20-ohm resistor. What is the current flowing through the circuit?

Accepted Answer

6 A

Answer

Using Ohm's Law: I = V/R = 120/20 = 6 amperes.

Question 5

What property of a material determines how well it conducts electricity?

Accepted Answer

Resistivity

Answer

Resistivity (ρ) is an intrinsic material property that determines electrical resistance; lower resistivity means better conductivity.

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