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

If 300 ohm resistors are wired in parallel, what is the total resistance?

1. 150 ohms

2. 300 ohms

3. 100 ohms

4. 200 ohms

The correct answer is: 100 ohms

When resistors are connected in parallel, the total or equivalent resistance can be calculated using the formula: \[ \frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + ... + \frac{1}{R_n} \] In this case, if we consider two resistors of 300 ohms wired in parallel, the calculation would be: \[ \frac{1}{R_{total}} = \frac{1}{300} + \frac{1}{300} = \frac{2}{300} \] This simplifies to: \[ R_{total} = \frac{300}{2} = 150 \text{ ohms} \] So, for two 300 ohm resistors in parallel, the total resistance is 150 ohms, which corresponds to the first option. The resulting value demonstrates how parallel resistors lower the overall resistance compared to the individual resistors, as the current has multiple pathways to flow through. This calculation can also be extended to more resistors in multiple configurations, but the key aspect within this instance is recognizing the parallel configuration leads to a total resistance that is always less than the