MCQ
A bar magnet has coercivity $4 \times 10^3 \mathrm{Am}^{-1}$. It is desired to demagnetise it by inserting it inside a solenoid 12 cm long and having 60 turns. The current that should be sent through the solenoid is
- A2 A
- B4 A
- C6 A
- ✓8 A
✓
Answer
Correct option: D.
8 A
(d) 8 A
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
The image which can be obtained on a screen is called:
Points $A$ and $B$ are situated along the extended axis of $2\, cm$ long bar magnet at a distance $x $ and $2x$ $ cm$ respectively. From the pole nearer to the points, the ratio of the magnetic field at $ A$ and $B$ will be
→An object $O$ is placed in front of a small plane mirror $M_1$ and $a$ large convex mirror $M_2$ of focal length $f$. The distance between $O$ and $M_1$ is $x$, and the distance between $M_1$ and $M_2$ is $y$. The images of $O$ formed by $M_1$ and $M_2$ coincide. The magnitude of $f$ is
→A magnet oscillating in a horizontal plane has a time period of 2 second at a place where the angle of dip is $30^{\circ}$ and 3 seconds at another place where the angle of dip is $60^{\circ}$. The ratio of resultant magnetic fields at the two places is
→In case of electrons and photons having the same wavelength. What is same for them?
The energy of a photon of a characteristic $X-$ray from a Coolidge tube comes from:
→An archaeologist analyses the wood in a prehistoric structure and finds that ${C^{14}}$ (Half life $= 5700\, years$) to ${C^{12}} $ is only one- fourth of that found in the cells buried plants. The age of the wood is about ........$years$
→$A$ brass disc and a carbon disc of same radius are assembled alternatively to make a cylindrical conductor. The resistance of the cylinder is independent of the temperature. The ratio of thickness of the brass disc to that of the carbon disc is [$\alpha$ is temperature coefficient of resistance and Neglect linear expansion ]
→The value of horizontal component of earth's magnetic field at a place is $0.35 \times 10^{-4} \,T$. If the angle of dip is $60^{\circ}$, the value of vertical component of earth's magnetic field is nearly ............. $\times 10^{-4} \,T$
→In helium nucleus, there are