Question 278: AC fundamentals

Question

A coil has inductance 2 H . The ratio of its reactance when it is connected first to an a.c. source and then to a d.c. source is

Accepted Answer

Step 1: Recall inductive reactance formula
For an inductor connected to an
a.c. source
of angular frequency $\omega$:
$ X_L = \omega L $
where $L$ is the inductance and $\omega = 2\pi f$.
Step 2: For a d.c. source ($f = 0$)
In d.c., frequency $f = 0 \implies \omega = 0$.
So,
$ X_{L,\;DC} = \omega L = 0 	imes L = 0 $
Step 3: For an a.c. source ($f 
eq 0$)
Then,
$ X_{L,\,AC} = \omega L $
is some finite positive value (for nonzero $\omega$).
Step 4: Ratio required
$ 	ext{Ratio} = \frac{X_{L,\;AC}}{X_{L,\;DC}} = \frac{\omega L}{0} $
That is division by zero, which tends to
$\infty$
.
Ã¢ÂÂ Final Answer:
Option C: $\infty$

Answer

-1

Answer

zero

Answer

$\infty$

Answer

+1

AC fundamentals

A coil has inductance 2 H . The ratio of its reactance when it is connected first to an a.c. source and then to a d.c. source is

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