Question

What is the SI unit of self-inductance?
A. Henry
B. Tesla
C. Weber
D. Gauss

Answer 1

Hint: SI unit the international unit of system which is accepted. Induction has two types: self-induction and mutual induction. In mutual induction, change of current in neighboring coils produces an e.m.f.

Complete step by step solution:
When a changing current flows through a coil, a changing magnetic field is produced. It gets linked with a coil and e.m.f is induced which opposes the change producing it.
The property of coil due to which it opposes a change in current flowing through the same coil is by inducing e.m.f is called self-induction.
When Steady Current I flows through a coil, it produces a magnetic flux $\phi $ and it is given by
$\phi \propto I$
Now remove proportionality sign
Therefore
$\phi =LI$-----------(1)
Where, L – self-inductance or coefficient of self-inductance.
If current is varying then induced e.m.f then according to Faraday’s law
$e=-L\dfrac{dI}{dt}$--------(2)
Now put value of equation (1) in equation (2),we get
$e=-L\dfrac{dI}{dt}$
Where,
E = induced e.m.f
Unit of $\dfrac{dI}{dt}$ is amp/sec and unit of e is volt (V)
Then $L=\dfrac{e}{\dfrac{dI}{dt}}$
So 1 unit of L = $\dfrac{1V}{1Amp/\sec }$
And $\dfrac{1V}{1Amp/\sec }$ is equal to 1 henry.
Thus, the self-inductance is defined as a magnitude of induced e.m.f in the coil when current changes at the rate of one amp/sec. Its SI unit is Henry (H).
Thus coil has a self-inductance of one henry when a current changes at the rate of 1 amp/sec inducing an e.m.f of one volt.
Option (A) is correct.

Note: Self-induction is nothing but change of current in coil and due to which a voltage or an e.m.f is induced in coil. International unit of the system of self-induction is Henry. Flux is defined as the number of magnetic lines passing through a given area due to which current is produced and then changing flux is produced.