# Maharashtra Board Class 11 Physics Chapter 12 Magnetism Solution

## Maharashtra Board Class 11 Physics Solution Chapter 12 – Magnetism

Balbharati Maharashtra Board Class 11 Physics Solution Chapter 12: Magnetism. Marathi or English Medium Students of Class 11 get here Magnetism full Exercise Solution.

 Std Maharashtra Class 11 Subject Physics Chapter 12 Chapter Name Magnetism

1.) Choose the correct option.

i) Let r be the distance of a point on the axis of a bar magnet from its center. The magnetic field at r is always proportional to

(A) 1/r2                      (B) 1/r3                   (C) 1/r            (D) not necessarily 1/r3 at all points

we have equation for magnetic field at a distance r on the axis of bar magnet from its centre AS

B= μ0M/(4πr3 )

Therefore magnetic field is proportional to 1/r3.

ii) Magnetic meridian is the plane

(A) Perpendicular to the magnetic axis of Earth

(B) Perpendicular to geographic axis of Earth

(C) Passing through the magnetic axis of Earth

(D) Passing through the geographic axis Earth

According to definition of magnetic meridian it is a plane perpendicular to surface of the Earth and passing through the magnetic axis. therefore answer C.

iii) The horizontal and vertical component of magnetic field of Earth are same at some place on the surface of Earth. The magnetic dip angle at this place will be

(A) 30o                  (B) 45 o

(C) 0 o                    (D) 90 o

We have magnetic dip angle as

Students.

tanφ=Bv/BH

as BV=BH

tanφ=1 Hence φ=450.

iv) Inside a bar magnet, the magnetic field lines

(A) are not present

(B) are parallel to the cross sectional area of the magnet

(C) are in the direction from N pole to S pole

(D) are in the direction from S pole to N pole

Outside the magnet magnetic lines are in the direction from N pole to S pole and inside the magnet magnet magnetic lines are in the direction from S pole to N pole.

v) A place where the vertical components of Earth’s magnetic field is zero has the angle of dip equal to

(A) 0o (B) 45 o

(C) 60 o (D) 90 o

We know that tan(φ) =Bv/BH

as BV=0

tan(φ) =0 Hence φ=0

vi) A place where the horizontal component of Earth’s magnetic field is zero lies at

(A) geographic equator

(B) geomagnetic equator

(C) one of the geographic poles

(D) one of the geomagnetic poles

Geomagnetic pole is the place where horizontal component of Earth’s magnetic field is zero.

vii) A magnetic needle kept nonparallel to the magnetic field in a non uniform magnetic field experiences

(A) a force but not a torque

(B) a torque but not a force

(C) both a force and a torque

(D) neither force nor a torque

A magnetic needle will experience force as well as torque.

2.) Answer the following questions in brief.

i) What happens if a bar magnet is cut into two pieces transverse to its length/ along its length?

if a bar magnet is cut into two pieces transverse to its length, two pieces are produced. These two pieces are two different magnets. New formed magnets will have same pole strength as original magnet but will have reduced magnetic length as its length is cut down during transverse cut.

if a bar magnet is cut into two pieces along its length, , two pieces are produced. These two pieces are two different magnets. New formed magnets will have same magnetic length as original magnet but will have reduced pole strength as its poles are divided into two parts.

ii) What could be the equation for Gauss’ law of magnetism, if a monopole of pole strength p is enclosed by a surface?

if a monopole of pole strength p is enclosed by a surface exists then gauss law of magnetism will be given by

∫ B.ds = μ0p

3.) Answer the following questions in detail.

i) Explain the Gauss’ law for magnetic fields.

Gauss law for electric field states that the net electric flux through a closed Gaussian surface is proportional to the net electric charge enclosed by the surface.

In analogous to this gauss law for magnetic field is given by the net magnetic flux ΦB through a closed Gaussian surface is zero, i.e

ΦB=∫ B.ds = 0.

Net flus is zero because if we draw any Gaussian surface net magnetic lines entering to surface and net lines exiting the surface are same.

ii) What is a geographic meridian? How does the declination vary with latitude? Where is it minimum?

A plane perpendicular to the surface of the Earth perpendicular to geographic axis is geographic meridian. Angle between the geographic and the magnetic meridian at a place is called ‘magnetic declination’ (α).

Declination is considered positive when the magnetic north is east of true north and Declination is considered negative when the magnetic north is west of true north.

iii) Define the Angle of Dip. What happens to angle of dip as we move towards magnetic pole from magnetic equator?