Magnetic Effects of Current - NEET Physics Questions
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Magnetic Effects of Current

Practice Questions:
Question 191: moderate

A bar magnet of magnetic moment \(\vec{M}\) is placed in a uniform magnetic field \(\vec{B}\) such that \(\vec{M}\) and \(\vec{B}\) are antiparallel. If the magnet is rotated through \(90^\circ\), then the work done on the magnet will be

1. \(-MB\)
2. \(\frac{-MB}{2}\)
3. \(2MB\)
4. \(\frac{MB}{2}\)
View Answer

Work done in rotating a magnetic dipole is \(W = MB(\cos \theta_1 - \cos \theta_2)\). Since initially \(\theta_1 = 180^\circ\) and finally \(\theta_2 = 90^\circ\), \(W = MB(\cos 180^\circ - \cos 90^\circ) = MB(-1 - 0) = -MB\).

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Question 192: easy

Consider the following statements:

Statement (A): All magnetism is due to circulating currents i.e. there cannot be magnetic field without current.

Statement (B):  The orbital magnetic moment of an electron in the ground state of a hydrogen atom is equal to one Bohr Magneton.

Choose the correct option.

1. Statement (A) is correct while statement (B) is incorrect.
2. Statement (B) is correct while statement (A) is incorrect.
3. Both the statements are correct
4. Both the statements are incorrect
View Answer

Statement (A) is incorrect because elementary particles like electrons have intrinsic spin magnetic moments not due to actual circulating currents. Statement (B) is correct as \(\mu_l = 1 \mu_B\) for ground state.

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