CBSE
Multiple Choice QuestionsElectromagnets are made of soft iron because soft iron has
low retenitivity and high coercive force
high retentivity and high coercive force
low retentivity and low coercive force
low retentivity and low coercive force
A wire carrying current I has the shape as shown in the adjoining figure. Linear parts of the wire are very long and parallel to X -axis while semicircular portion of radius R is lying in a Y-Z plane. The magnetic field at point O is.
There are four light -weight rod samples A, B, C D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted
(i) A is feebly repelled
(ii) B is feebly attracted
(iii) C is strongly attracted
(iv) D remains unaffected
C is a diamagnetic material
D is of a ferromagnetic material
A is of a non- magnetic material
A is of a non- magnetic material
A bar magnet of length l and magnetic dipole moment M is bent in the form of an arc as shown in figure, The new magnetic dipole moment will be
M
3M/π
2M/π
2M/π
The magnetic susceptibility is negative for,
a paramagnetic material only
ferromagnetic material only
paramagnetic and ferromagnetic materials
paramagnetic and ferromagnetic materials
A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. it
will become rigid showing no movement
will stay in any position
will stay in the north-south direction only
will stay in the north-south direction only
Two identical long conducting wire AOB and COD are placed at right angle to each other, with one above other such that O is their common point for the two. The wires carry I1 and I2 currents, respectively. point P is lying at distance d from O along a direction perpendicular to the plane containing the wires. The magnetic field at the point P will be,
A thin ring of radius R metre has charge q column uniformly spread on it. The ring rotates about its axis with a constant frequency of f revolution/s. The value of magnetic induction in Wb m-2 at the centre of the ring is
μoq f/ 2π R
μoq / f 2π R
μoq / 2 f R
μoq / 2 f R
A vibration magnetometer placed in magnetic meridian has a small bar magnet. The magnet executes oscillations with a time period of 2s in earth's horizontal magnetic field of 24 μT. When a horizontal field of 18 μT is produced opposite to the earth's field by placing a current-carrying wire, the new time period of magnet will be
1s
2s
3s
3s
Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole moments m. Which configuration has highest net magnetic dipole moment?
