GP Magnetism

Which statements about magnetic field lines is not correct

Which one of the following statements about magnetic field lines is not correct?

They can emanate from a point
They do not cross each other
Field lines between two poles cannot be precisely straight lines at the ends
There are no filed lines within a bar magnet

What is the net force experienced by a bar magnet

What is the net force experienced by a bar magnet placed in a uniform magnetic field?

Zero
Depends upon length of the magnet
Never zero
Depends upon temperature

A current-carrying wire is known to produce magnetic lines of force

A current-carrying wire is known to produce magnetic lines of force around the conducting straight wire. The direction of the lines of force may be described by

left-hand thumb rule for up-current and right-hand thumb rule for down current
right-hand thumb rule for both up and down currents
right-hand thumb rule for up-current and left-hand thumb rule for down current
left-hand thumb rule for both up and down currents

A cyclotron accelerates particles of mass m and change q

A cyclotron accelerates particles of mass m and change q. The energy of particles emerging is proportional to

q/m²
q²/m
q²/m²
q

A force F, acting on an electric charge q, in presence of an electromagnetic field

A force F, acting on an electric charge q, in presence of an electromagnetic field, moves the charge parallel to the magnetic field with velocity v. Then F is equal to (where E and B are electric field and magnetic field respectively)

q(v x B)
q(v x E)
qB
qE

Which devices changes low voltage alternating current to high voltage

Which one of the following devices changes low voltage alternating current to high voltage alternating current and vice versa?

Generator
Motor
Transformer
Vibrator

At which place Earth’s magnetic field becomes horizontal

At which place Earth’s magnetic field becomes horizontal?

Magnetic meridian
Magnetic equator
Geographical pole
Tropic of Cancer

Step-up transformers are used for

increasing electrical power
decreasing electrical power
decreasing voltage
increasing voltage

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 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

A constant current flows in a horizontal wire in the plane of the paper

A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in Figure. 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

In the arrangement there are two coils wound on a non-conducting cylindrical rod

In the arrangement shown in Figure 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

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

A uniform magnetic field exists in the plane of paper pointing from left to right

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in Figure. 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

For a current in a long straight solenoid N- and S-poles are created at the two ends

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 circular loop placed in a plane perpendicular to the plane of paper

A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti clockwise and clockwise respectively. 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

If the key in the arrangement is taken out and magnetic field lines are drawn

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

North pole of a magnet can be identified by

Another magnet having its poles marked as North pole and South pole.
Another magnet no matter whether the poles are marked or not.
Using an iron bar.
Using iron filings.