309A Circuit Theory and Calculations 4

Question 1

What is Kirchhoff's Voltage Law (KVL)?

Accepted Answer

The sum of all voltages around a closed loop equals zero

Answer

Kirchhoff's Voltage Law states that the algebraic sum of all voltage drops and rises around any closed loop in a circuit must equal zero, reflecting conservation of energy.

Question 2

A 10 kW, 240 V single-phase load operates for 8 hours. How many kWh of energy are consumed?

Accepted Answer

80 kWh

Answer

Energy = Power × Time = 10 kW × 8 hours = 80 kWh. Energy consumption is the product of power and the duration of use.

Question 3

What is the phase angle between voltage and current in a purely capacitive circuit?

Accepted Answer

90° (current leads voltage)

Answer

In a purely capacitive circuit, current leads voltage by 90°. This is remembered by the mnemonic 'ICE' — In a Capacitor, current (I) leads voltage (E).

Question 4

What is the total resistance of four 100 Ω resistors connected in parallel?

Accepted Answer

25 Ω

Answer

For identical resistors in parallel: Rt = R/n = 100/4 = 25 Ω. The total resistance is always less than the smallest individual resistor.

Question 5

A transformer has a turns ratio of 10:1. If the primary voltage is 4800 V, what is the secondary voltage?

Accepted Answer

480 V

Answer

Secondary voltage = Primary voltage / Turns ratio = 4800 / 10 = 480 V. A step-down transformer reduces voltage by the turns ratio.

Red Seal Electrician 309A Practice Test

Red Seal Electrician 309A Practice Test

309A Circuit Theory and Calculations 4