A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by $60^{\circ}$ is $W$. Now the torque required to keep the magnet in this new position is
- $\frac{W}{\sqrt{3}}$
- $\sqrt{3} W$
- $\frac{\sqrt{3} W}{2}$
- $\frac{2W}{\sqrt{3}}$
The Correct Option is B
Solution and Explanation
Work and Torque Calculation
Let's start with the calculation of work (W) and torque (τ) for the given situation.
Work Calculation:
Work is calculated as:
\(W = MB \left(\cos 0^{\circ} - \cos 60^{\circ}\right)\)
Substituting the values for cosine:
\(W = MB \left(1 - \frac{1}{2}\right) = \frac{MB}{2}\)
Torque Calculation:
The required torque for this position is:
\(τ = MB \sin θ\)
Substituting the value for sine of 60°:
\(τ = MB \sin 60^{\circ} = \frac{\sqrt{3}}{2} MB = \sqrt{3} W\)
Conclusion:
Therefore, the required torque is \(τ = √3 W\).
Top Questions on Magnetism and matter
- What is/are the primary effect(s) of applying upward continuation to magnetic field data?
- GATE GG - 2025
- Geology and Geophysics
- Magnetism and matter
- When an external magnetic field of strength \(1.5 \times 10^{-3}\) A/m is applied to a rock sample, the measured intensity of magnetization is \(0.5 \times 10^{-3}\) A/m. The magnetic susceptibility of this rock is ________ (Round off to two decimal places).
- GATE GG - 2025
- Geology and Geophysics
- Magnetism and matter
- Identify the correct statement:
- KCET - 2025
- Physics
- Magnetism and matter
- Two long parallel wires X and Y, separated by a distance of 6 cm, carry currents of 5 A and 4 A, respectively, in opposite directions as shown in the figure. Magnitude of the resultant magnetic field at point P at a distance of 4 cm from wire Y is \( 3 \times 10^{-5} \) T. The value of \( x \), which represents the distance of point P from wire X, is \_\_\_\_\_ cm. (Take permeability of free space as \( \mu_0 = 4\pi \times 10^{-7} \) SI units.) \includegraphics[width=1\linewidth]{126.png}
- JEE Main - 2025
- Physics
- Magnetism and matter
- A diamagnetic substance is brought, one by one, near the north pole and the south pole of a bar magnet. It is:
- CBSE CLASS XII - 2025
- Physics
- Magnetism and matter
Questions Asked in NEET exam
In a Vernier caliper, \(N+1\) divisions of vernier scale coincide with \(N\) divisions of main scale. If 1 MSD represents 0.1 mm, the vernier constant (in cm) is:
- NEET (UG) - 2024
- Units, Dimensions and Measurements
- In an ecosystem if the Net Primary Productivity (NPP) of first trophic level is 100x (kcal m-2)yr-1, what would be the GPP (Gross Primary Productivity) of the third trophic level of the same ecosystem?
- NEET (UG) - 2024
- Ecosystems
- Two bodies A and B of same mass undergo completely inelastic one dimensional collision. The body A moves with velocity v1 while body B is at rest before collision. The velocity of the system after collision is v2. The ratio v1 : v2 is :
- NEET (UG) - 2024
- Average Velocity and Instantaneous Velocity
- A bob is whirled in a horizontal plane by means of a string with an initial speed of ω rpm. The tension in the string is T. If speed becomes 2ω while keeping the same radius, the tension in the string becomes:
Identify the major product C formed in the following reaction sequence:
- NEET (UG) - 2024
- Chemical Reactions
Concepts Used:
Magnetism & Matter
Magnets are used in many devices like electric bells, telephones, radio, loudspeakers, motors, fans, screwdrivers, lifting heavy iron loads, super-fast trains, especially in foreign countries, refrigerators, etc.
Magnetite is the world’s first magnet. This is also called a natural magnet. Though magnets occur naturally, we can also impart magnetic properties to a substance. It would be an artificial magnet in that case.
Read More: Magnetism and Matter
Some of the properties of the magnetic field lines are:
- The lines and continuous and outside the magnet, the field lines originate from the North pole and terminate at the South pole
- They form closed loops traversing inside the magnet.
- But here the lines seem to originate from the South pole and terminate at the North pole to form closed loops.
- More number of close lines indicate a stronger magnetic field
- The lines do not intersect each other
- The tangent drawn at the field line gives the direction of the field at that point.