Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

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In a parallel circuit with resistors R1=30 ohms, R2=15 ohms, and R3=10 ohms, if the current through R2 is 4 amperes, what is the source voltage?

30 volts
60 volts
75 volts
100 volts

The correct answer is: 60 volts

To determine the source voltage in a parallel circuit, you can use Ohm's law, which states that Voltage (V) = Current (I) × Resistance (R). In this scenario, you are given the current flowing through resistor R2, which is 4 amperes. Since R2 has a resistance of 15 ohms, you can calculate the voltage across R2 using the mentioned formula: V = I × R V = 4 A × 15 Ω V = 60 V In a parallel circuit, the voltage across all components is the same. Therefore, the source voltage, which is equal to the voltage across R2, is 60 volts. This relationship is key in parallel circuits, where each branch experiences the same voltage drop as the source. This reasoning demonstrates that the source voltage is indeed 60 volts, confirming that this is the correct choice.