PC General Theory and Calculations 2

Question 1

A 240V single-phase circuit draws 15A. What is the apparent power in VA?

Accepted Answer

3,600 VA

Answer

Apparent power S = V × I = 240V × 15A = 3,600 VA.

Question 2

Which formula correctly expresses Ohm's Law for current?

Accepted Answer

I = V / R

Answer

Ohm's Law states I = V / R, where I is current, V is voltage, and R is resistance.

Question 3

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

Accepted Answer

2 Ω

Answer

1/R_T = 1/6 + 1/12 + 1/4 = 2/12 + 1/12 + 3/12 = 6/12, so R_T = 2Ω.

Question 4

What is the power factor of a purely resistive AC circuit?

Accepted Answer

1.0

Answer

A purely resistive circuit has zero phase angle between V and I, so PF = cos(0°) = 1.0.

Question 5

A conductor has a resistance of 0.5Ω and carries 20A. What is the power dissipated as heat?

Accepted Answer

200 W

Answer

P = I² × R = (20)² × 0.5 = 400 × 0.5 = 200 W.

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