Magnetism and Matter Test 20

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Magnetism and Matter Test 20

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Question 1
1 / -0

Choose the correct statement for the following

A
Magnetic lines give direction of magnetic field while electric field lines do not

B
Electric lines give direction of electric field while magnetic field lines do not

C
Electric lines of force are closed curves but not magnetic lines of force

D
Magnetic field lines are closed curved but electric field lines are not

Solution

Both magnetic lines and electric lines give direction of magnetic field and electric field respectively.
Electric lines of force can closed curves but only in case of an electric dipole. Otherwise they can take any form and direction except that two or more lines cannot intersect each other.
Magnetic field lines are always closed curved only because separate noth and south poles do not exist. We always get a pair only.
Question 2
1 / -0

Which of the following can be used to lift giant industrial machines?

A
electromagnets

B
permanent magnets

C
both A and B

D
none of the above

Solution

An electromagnetic crane is a type of crane with an electromagnetic lift. Electromagnetic cranes are commonly utilized in lifting and moving various scrap metals. It does not have the mechanical 'pincers' of a regular crane, instead, it has a large flat magnet which draws the metallic materials to it.
Using the principle of electromagnetic induction, these large machines are used to handle scrap ferrous metals, such as iron and steel, which can be found in junk yards and recycling plants.
Question 3
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Magnetic lines of force

A
Always intersect

B
Are closed curves

C
Tend to crowd far away from the poles of a magnet

D
Do not pass through vacuum

Solution

Magnetic lines of force are the imaginary lines in a magnetic field which show us the path along which a single notrh pole will move.
They can never intersect. Otherwise at the junction point, the north pole will have two directions to move simultaenously. How can any particle move along two paths at a time?
Isolated single monopoles do not exist. We always get a pair of north and south pole only. The lines of force start from a north pole and end at a south pole.
Hence magnetic lines of force are always closed curves.
They are crowded where the field is strong and are less and far from each other where the field is weak. Far away from the poles of a magnet, the field is very weak. Hence over there they won't tend to crowd, but remain away from each other.
They can easily pass through vacuum.
Thus B is the only correct option.
Question 4
1 / -0

The space around the magnet in which another magnetic pole placed experiences a magnetic force is _________.

A
Magnetic field

B
Magnetic moment

C
Polarized space

D
None of the above

Solution

As the surrounding around a magnet has its field which represent the magnetic attractive or repulsive force,thus the region where this force is experienced is termed as magnetic field as this force is due to magnet.
Question 5
1 / -0

Once the applied electric current is removed, the electromagnet :

A
retains its magnetism

B
loses its magnetism

C
gets magnetized in opposite direction

D
none of the above

Solution

The soft iron inside the coil makes the magnetic field stronger because it becomes a magnet itself when the current is flowing. Soft iron is used because it loses its magnetism as soon as the current stops flowing since it has low retentivity.
Question 6
1 / -0

The magnetic lines of force due to a bar magnet are

A
Curved lines

B
Curved closed loops

C
Concentric circles

D
Parallel and straight

Solution

The magnetic lines of force due to a bar magnet are closed loops. The field lines are directed from the north pole to the south pole outside the magnet. The field lines are directed from the south pole to the north pole inside the magnet.
Question 7
1 / -0

The magnetic field lines due to a bar magnet correctly shown are:

A

B

C

D

Solution

As the magnetic field lines are closed curves.
Thus they must pass through the magnets as well and its direction is from south to north for same sense (direction)
Question 8
1 / -0

At what temperature $$(^0C)$$, in the case of mercury (Hg) drops abruptly to zero?

A
3.2 K

B
4.2 K

C
5.2 K

D
6.2 K

Solution

Mercury becomes a superconductor at $$4.2K$$ and at that temperature its resistance becomes zero.

Answer-(B)
Question 9
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The critical temperature for superconductors is the temperature at which the electrical resistivity of a metal

A
drops to zero

B
increase to maximum limit

C
decrease to a certain limit

D
none of the above

Solution

The critical temperature is the temperature at which the resistivity of a conductor becomes $$0$$.

Answer-(A)
Question 10
1 / -0

A straight wire is carrying an electric current :

A
There are no magnetic lines of force near the wire

B
There are lines of force and they are circular lines encircling the wire

C
The lines of force are straight lines parallel to the wire and in the direction opposite to the current

D
The lines of force are straight lines parallel to the wire in the direction opposite to the current.

Solution

The direction of line of forces of magnetic field produced by a current carrying wire can be obtained by using maxwell's right hand thumb .By holding the thumb along the the direction of current then the direction in which your finger encircle the wire will give the direction of magnetic line of forces .