Magnetic Effects of Current

Question 1

what is a compass needle

Answer 1

It is a small bar magnet that is free to rotate on a horizontal plane or pivot. The ends of the compass needle point approximately towards
north and south directions.The End of the needle pointing towards north is called north pole. The end of the needle pointing towards south pole.

Question 2

define a magnetic force

Answer 2

the force with which a pole of a magnet attracts or repels the pole of another magnet is called magnetic force.

Question 3

define magnetic field

Answer 3

The space around a magnet within which its influence can be felt or the magnetic force can be detected by another magnet or magnetic substance is called a magnetic field. It is denoted by B.

Question 4

what is a magnetic field line

Answer 4

It is a curve around a magnet such that the tangent at any point on the curve gives the direction of magnetic field at tht point. It is helpful show us the direction and intensity of magnetic field. It a representation of magnetic field

Question 5

is magnetic field a scalar or vector quantity

Answer 5

Magnetic field is a physical quantity that has both direction and alwell as magnitude. Hence it is vector quanitity.

Question 6

how do we determine the direction of magnetic field

Answer 6

The direction of the magnetic field is taken to be the direction in which a
north pole of the compass needle moves inside it. Therefore it is taken
by convention that the field lines emerge from north pole and merge at
the south pole
Inside the magnet, the direction of field lines is from its south pole to its
north pole. Thus the magnetic field lines are closed curves

Question 7

how do we determine the strength of magnetic field

Answer 7

The relative strength of the magnetic field is shown by the degree of
closeness of the field lines. The field is stronger, that is, the force acting
on the pole of another magnet placed is greater where the field lines are crowded.

Question 8

define strong and weak magnetic field

Answer 8

i) when the magnetic field lines are very close to each other or very crowded, then the magnetic field in that region is said to be atrong. It is strong near the poles of magnet.

ii) when the magnetif fields are placed very far away from each other, then the magnetic field in that region is said to be weak. It is weak away from the magnet.

Question 9

what are the properties of field lines

Answer 9

i) Magnetic fields lines form closed continuous curves.

ii) They emerge from the north pole of the magnet and merge at the south pole. inside the magnet they go from south pole to north pole.

iii) No two magnetic field lines can intersect each other. The tangent at any point on the curve gives the direction of magnetic field at that point. If two filed linesinstersect then there will be two tangents at that point and two directions of magnetic field which is not possible.

iv) The relative strength of magnetic field depend upon the degree of closeness of magnetic fields lines

extra:
v) The tangent at any point on the curve gives the direction of magnetic field at that point.

Question 10

what is magnetic effect of electric current?

Answer 10

An electric current flowing through a conductor produces a magnetic field in the space around it. This is is called magnetic effects of current

Question 11

Why does a compass needle get deflected when brought near a bar magnet?

Answer 11

i)compass needle is a small magnet which experiences a force in the magnetic field of a bar magnet
ii) the bar magnet exerts a force on both poles of a compass neelde which are equal and opposite.

Question 12

how is the magnetic field lines when current passes through a straight conductor

Answer 12

i) The iron fillings arrange themselves in concentric circles with the wire being the centre.
ii) Hence, the shape of magnetic field lines produced around a conductor carrying current is concentric circles. The distance between circles increases with distance.

Question 13

what are the factors on which intensity of electric current through a conductor carryign current depends on?

Answer 13

i) Current flowing hrough a conductor
When the current flowing through the conuctor is increased with the help of rheostat, the deflection of the needle of the magnetic compass placed next to the conductor inceases. Similarly, when the current flowing through the conducto decreases the deflection of the needle placed near the conductor decreases. The current flowing through the conductor is directly proportional to the intensity of magnetic field.

ii) The distance from the conductor
When the magnetic compass is placed close to the conductor, then the deflection in the needle of the compass is very large, But when the compass is placed very far from the current carrying conductor, then the deflection of the needle is very small. So deflection decreases with distance. So the intensity of the magentic field is inversely proportional to the distance from current-carryng conductor.

Question 14

what happens when direction of current is changed

Answer 14

The deflection in the needle becomes opposite when the direction of the current is reversed.

Question 15

what is right hand thumb rule?

Answer 15

Imagine that you are holding a current-carrying straight
conductor in your right hand such that the thumb points towards
the direction of current. Then your fingers will wrap around the
conductor in the direction of the field lines of the magnetic field, as
shown in Fig. 13.7. This is known as the right-hand thumb rule*

Question 16

explain the magnetic field around a current carrying loop?

Answer 16

We know that the magnetic field produced
by a current-carrying straight wire depends inversely on the
distance from it. Similarly at every point of a current-carrying
circular loop, the concentric circles representing the magnetic
field around it would become larger and larger as we move
away from the wire (Fig. 13.8). By the time we reach at the
centre of the circular loop, the arcs of these big circles would
appear as straight lines. Every point on the wire carrying
current would give rise to the magnetic field appearing as
straight lines at the center of the loop. By applying the right
hand rule, it is easy to check that every section of the wire
contributes to the magnetic field lines in the same direction
within the loop.

Question 17

how does magnetic field through a circular loop depend upon number of coils?

Answer 17

the magnetic field produced by a current-carrying
wire at a given point depends directly on the current passing through it.
Therefore, if there is a circular coil having n turns, the field produced is
n times as large as that produced by a single turn. This is because the
current in each circular turn has the same direction, and the field due to each turn then just adds up.

Question 18

what does the magnetic field produced by a circular loop depend upon

Answer 18

i) The strength of magnetic field porudced by a circular loop is directly proportional to the amount of current flwoing through the loop.

ii) The= strength of the magnetic field produced by a circular loop at the centre in invsersely proportional to the radiu of the wire

iii) The strength of mangnetic field produced at the centre by a circular coil is direclty proportional to the number of turns of the wire

Question 19

define solenoid

Answer 19

A coil of many circular turns of insulated copper wire wrapped
closely in the shape of a cylinder is called a solenoid.

Question 20

how does current pass through a solenoid?

Answer 20

One end of the solenoid acts like a north pole while the other end acts like a south pole of a bar magnet. When the current moves in the clockwise direction when seen from one end-on, this end is the south pole. When the current moves in the anticlockwise direction when seen from one end on, this end is called the north pole.

Question 21

how does a solenoid replicate the bar magnet

Answer 21

In fact, one end of the solenoid
behaves as a magnetic north pole, while the other behaves as the
south pole. The field lines inside the solenoid are in the form of
parallel straight lines. This indicates that the magnetic field is
the same at all points inside the solenoid. That is, the field is
uniform inside the solenoid.

Question 22

charcaacteristics of magnetic field inside solenoid

Answer 22

i) The magnetic field inside a solenoid is unifrom ( same at all points) and it sstrong Thsi means that the lines of magnetic field are striaght parallel and very close to each other,

ii) in a long solenoid, the magnetic field starts decreasing towards the ends because near to the ends the magnetic fields start spreading

iii) magnetic field outside solenoid is very weak and not uniform

iv) Outside the magnet, the magnetic field lines are from north to south pole while inisde they are from south to north pole

v) magnetic field of solenoid resenbles magnet.

vi)divergence of magnetic field indicate the decreasing strength og mag field at the end