Choose the incorrect statement from the following regarding magnetic lines of field
The direction of magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points
Magnetic field lines are closed curves
If magnetic field lines are parallel and equidistant, they represent zero field strength
Relative strength of magnetic field is shown by the degree of closeness of the field lines
If the key in the arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are
concentric circles
elliptical in shape
straight lines parallel to each other
concentric circles near the point O but of elliptical shapes as we go away from it
A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to
A
B
A if the current is small, and B if the current is large
B if the current is small and A if the current is large
For a current in a long straight solenoid N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is
The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid
The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil
The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet
The N- and S-poles exchange position when the direction of current through the solenoid is reversed
A uniform magnetic field exists in the plane of paper pointing from left to right. In the field an electron and a proton move as shown. The electron and the proton experience
forces both pointing into the plane of paper
forces both pointing out of the plane of paper
forces pointing into the plane of paper and out of the plane of paper, respectively
force pointing opposite and along the direction of the uniform magnetic field respectively
Commercial electric motors do not use
an electromagnet to rotate the armature
effectively large number of turns of conducting wire in the current carrying coil
a permanent magnet to rotate the armature
a soft iron core on which the coil is wound
In the arrangement shown there are two coils wound on a non-conducting cylindrical rod. Initially the key is not inserted. Then the key is inserted and later removed. Then
the deflection in the galvanometer remains zero throughout
there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed
there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction
there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions
Choose the incorrect statement
Fleming's right-hand rule is a simple rule to know the direction of induced current
The right-hand thumb rule is used to find the direction of magnetic fields due to current carrying conductors
The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically
In India, the AC changes direction after every 1/50 second
A constant current flows in a horizontal wire in the plane of the paper from east to west. The direction of magnetic field at a point will be North to South
directly above the wire
directly below the wire
at a point located in the plane of the paper, on the north side of the wire
at a point located in the plane of the paper, on the south side of the wire
The strength of magnetic field inside a long current carrying straight solenoid is
more at the ends than at the centre
minimum in the middle
same at all points
found to increase from one end to the other
To convert an AC generator into DC generator
split-ring type commutator must be used
slip rings and brushes must be used
a stronger magnetic field has to be used
a rectangular wire loop has to be used
The most important safety method used for protecting home appliances from short circuiting or overloading is
earthing
use of fuse
use of stabilizers
use of electric meter