Applied Electrical Calculations Flashcards

Using Ohm's Law, what is the current in a circuit with a voltage of 120 volts and a resistance of 24 ohms?

Answer: 5 A

Ohm's Law: I = V ÷ R. Current = 120 ÷ 24 = 5 amperes. Ohm's Law relates voltage (V), current (I), and resistance (R) with the formula V = I × R.

Two resistors of 8 ohms each are connected in series. What is the total resistance?

Answer: 16 ohms

In a series circuit, resistances add directly: R_total = R1 + R2 = 8 + 8 = 16 ohms. Current must flow through each resistor in sequence, so their resistance values accumulate.

An elevator motor operates at 240 volts and draws 20 amperes of current. What is its power consumption in watts?

Answer: 4,800 watts

Power (P) = Voltage (V) × Current (I). P = 240 × 20 = 4,800 watts. Power is measured in watts and represents the rate at which electrical energy is consumed.

A wire with a resistance of 2 ohms carries a current of 6 amperes. What is the voltage drop across the wire?

Answer: 12 V

Using Ohm's Law: V = I × R = 6 × 2 = 12 volts. The voltage drop across the wire represents energy lost to resistance in that conductor.

Two resistors of 6 ohms and 3 ohms are connected in parallel. What is the total resistance?

Answer: 2 ohms

For parallel resistors: 1/R_total = 1/R1 + 1/R2 = 1/6 + 1/3 = 1/6 + 2/6 = 3/6 = 1/2. Therefore R_total = 2 ohms. Parallel circuits provide multiple current paths, reducing total resistance.

A 480-watt motor runs on 120 volts. What current does it draw?

Answer: 4 A

Rearranging the power formula P = V × I gives I = P ÷ V. Current = 480 ÷ 120 = 4 amperes. This is a common calculation when sizing wiring or breakers for electrical equipment.