Question: Q. 7. Draw the magnetic field lines due to a current passing through a long solenoid. Use Ampere’s circuital law, to obtain the expression for thremagnetic field due to the current $I$ in a long solenoid having $n$ number of turns per unit length.
U[Comptt. Delhi I, II, III 2014]
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Solution:
Ans.
Alternatively,
Applying Ampere’s circuital law for the rectangular loop $a b c d a$
$$ \begin{aligned} \oint \vec{B} \cdot \overrightarrow{d l} & =\mu_{0} I \ B h & =\mu_{0} I(n h) \ B & =\mu_{0} n I \end{aligned} $$
[CBSE Marking Scheme 2014]
Answering Tip
- Distinctly understand the application of Biot-Savart’s law and Ampere’s circuital law.
