IEC Electrical Theory and Principles 4

Question 1

A conductor carrying current is placed in a magnetic field. The resulting force on the conductor is described by:

Accepted Answer

The Left-Hand Rule (motor action)

Answer

The Left-Hand Rule (Fleming's) determines the direction of force on a current-carrying conductor in a magnetic field (motor action).

Question 2

What is the effect of increasing wire gauge number (AWG) on conductor resistance?

Accepted Answer

Resistance increases

Answer

Higher AWG numbers indicate smaller diameter conductors, which have higher resistance per unit length.

Question 3

Which of the following is true about apparent power in an AC circuit?

Accepted Answer

It is the product of RMS voltage and RMS current

Answer

Apparent power (S) in volt-amperes (VA) equals the product of RMS voltage and RMS current: S = Vrms × Irms.

Question 4

Lenz's Law is best described as:

Accepted Answer

The induced EMF drives a current that opposes the change causing it

Answer

Lenz's Law states that the induced current flows in a direction to oppose the change in magnetic flux that caused it.

Question 5

What is the resonant frequency of a series LC circuit with L = 50 mH and C = 20 µF?

Accepted Answer

159 Hz

Answer

fr = 1/(2π√LC) = 1/(2π√(0.05 × 20×10⁻⁶)) ≈ 159 Hz.

IEC - Independent Electrical Contractors Practice Test