JEE Mains · Physics · STD 12 - 5. Magnetism and matter
The coercivity of a small magnet where the ferromagnet gets demagnetized is \(3 \times 10^3\) \( Am^{-1}\) The current required to be passed in a solenoid oflength \(10\ cm\) and number of turns \(100\), so that the magnet gets demagnetized when inside the solenoid, is
- A \(60\) \(mA\)
- B \(3\) \(A\)
- C \(6\) \(A\)
- D \(30\) \(mA\)
Answer & Solution
Correct Answer
(B) \(3\) \(A\)
Step-by-step Solution
Detailed explanation
Magnetic field in solenoid \(B=\mu_{0} n \mathrm{i}\) \(\Rightarrow \frac{B}{\mu_{0}}=n i\) (Where \(n=\) number of turns per unit length) \(\Rightarrow \frac{B}{\mu_{\theta}}=\frac{N i}{L}\) \(\Rightarrow 3 \times 10^{3}=\frac{100 i}{10 \times 10^{-2}}\)…
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