Exams › JEE Main › Physics

A bar magnet of length 6 cm has a magnetic moment of 4 J T^-1. Find the strength of magnetic field at a distance of 200 cm from the centre of the magnet along its equatorial line. (1) 4 × 10^-8 tesla (2) 3.5 × 10^-8 tesla (3) 5 × 10^-8 tesla (4) 3 × 10^-8 tesla

1. 4 × 10^-8 tesla
2. 3.5 × 10^-8 tesla
3. 5 × 10^-8 tesla
4. 3 × 10^-8 tesla

Correct answer: 5 × 10^-8 tesla

Solution

The strength of the magnetic field at a distance from a bar magnet can be calculated using the formula for the magnetic field along the equatorial line, which depends on the magnetic moment and the distance from the magnet. In this case, the calculations yield a value of 5 × 10^-8 tesla, confirming that option C is correct.

Related JEE Main Physics questions

• The SI unit weber is used for measuring which of the following quantities?
• Two identical magnetic dipoles, each having magnetic moment $1.0\ \text{A·m}^2$, are kept 2 m apart with their axes mutually perpendicular. The magnetic field at the midpoint between them is
• A material has relative permittivity $\varepsilon_r$ and relative permeability $\mu_r$. For a diamagnetic substance, which pair of values is physically permissible?
• A bar magnet freely suspended in the horizontal component of Earth’s magnetic field $H$ has a time period of 4 s. If a second magnet is placed nearby and the time period becomes 2 s, then the magnetic field produced by the second magnet is:
• A magnetic compass needle has a magnetic moment of 60 A·m² and is aligned along the geographical north at a certain location. If the torque acting on it is $1.2\times10^{-3}$ N·m and the horizontal component of Earth’s magnetic field at that place is 40 microtesla, what is the dip angle there?
• Which magnetic properties should the core material possess to be suitable for an electromagnet?

⚔️ Practice JEE Main Physics free + battle 1v1 →