Which of the following is NOT an application of Ohm's law?

• A. Computing the equivalent resistance of two resistors in parallel using $\frac{1}{R_e}=\frac{1}{R_1}+\frac{1}{R_2}$
• B. Determining the voltage drop across a resistor using $V=IR$ when current and resistance are known
• C. Finding resistance from measurements using $R=\frac{V}{I}$ for an ohmic device
• D. Calculating current using $I=\frac{V}{R}$ for a resistor with known voltage and resistance

Answer: (A)

Verified step by step guidance

1. Recall that Ohm's law states the relationship between voltage (V), current (I), and resistance (R) as \(V = I \times R\). This law applies to ohmic devices where resistance remains constant.
2. Identify which options directly use Ohm's law formulas: calculating voltage drop (\(V = I \times R\)), finding resistance (\(R = \frac{V}{I}\)), and calculating current (\(I = \frac{V}{R}\)) all come directly from Ohm's law.
3. Understand that computing the equivalent resistance of two resistors in parallel uses the formula \(\frac{1}{R_e} = \frac{1}{R_1} + \frac{1}{R_2}\), which is derived from circuit analysis principles, not directly from Ohm's law.
4. Recognize that while Ohm's law relates voltage, current, and resistance for a single resistor, the formula for equivalent resistance in parallel is a separate concept involving how resistors combine in circuits.
5. Conclude that the application NOT based on Ohm's law is the calculation of equivalent resistance for resistors in parallel, as it involves combining resistances rather than applying the \(V = IR\) relationship.