Question

If $L$ is the inductance and $R$ is the resistance then the SI unit of $\frac{L}{R}$ is

• A. second
• B. volt
• C. ampere
• D. per second

Hint:

$L/R$ (Inductive) and $RC$ (Capacitive) both have units of time (seconds).

Answer 1

The Correct Option is A

Step 1: Concept
The ratio $L/R$ is known as the inductive time constant ($\tau$) of an RL circuit.

Step 2: Meaning
Since it is a time constant, its dimensions must be that of time.

Step 3: Analysis
Unit of $L$ is Henry ($V \cdot s / A$) and unit of $R$ is Ohm ($V/A$).
$\frac{L}{R} = \frac{V \cdot s / A}{V/A} = s$.

Step 4: Conclusion
The SI unit of $L/R$ is the second. Final Answer: (A)