CBSE Class 12 Physics Chapter-4 Important Questions – Free PDF Download
Free PDF download of Important Questions with Answers for CBSE Class 12 Physics Chapter 4 – Moving Charges and Magnetism 2 Marks Questions prepared by expert Physics teachers from latest edition of CBSE(NCERT) books only by CoolGyan to score more marks in CBSE board examination.
CBSE Class 12 Physics Chapter-4 Important Questions
CBSE Class 12 Physics Important Questions Chapter 4 – Moving Charges and Magnetism
2 Marks Questions
1. A steady current flows in the network shown in the figure. What will be the magnetic field at the centre of the network?
Ans. Zero, because magnetic field at the centre of the loop is just equal and opposite i.e. magnetic field due 1- PQR is equal and opposite to that of PSR.
2. An 
– particle and a proton are moving in the plane of paper in a region where there is uniform magnetic field B directed normal to the plane of paper. If two particles have equal linear momenta, what will be the ratio of the radii of their trajectories in the field?
Ans. Since radius of the path (R) = 
=> R
=> 
=> R : Rp = 1:2.
3. Give one difference each between diamagnetic and ferromagnetic substances. Give one example of each?
Ans. Diamagnetic substances are weakly repelled by a magnet eg. Gold.
Ferromagnetic materials are strongly attracted by a magnet eg. Iron.
4. Write the expression for the force acting on a charged particle of charge q moving with velocity is in the presence of magnetic field B. Show that in the presence of this force.
(a) The K.E. of the particle does not change.
(b) Its instantaneous power is zero.
Ans. Since F = q (
)
(a) Since direction of force is perpendicular to the plane containing 
)
=> w = Fs cos
w = Fs 
= 0
=> KE = 0
KE will not – change
(b) since p = Fvcos = Fv = 0
=> Instantaneous power is also zero.
5. An electron of kinetic energy 25KeV moves perpendicular to the direction of a uniform magnetic field of 0.2 millitesla calculate the time period of rotation of the electron in the magnetic field?
Ans. B = 0.2 T = 0.2
10-3T
Time Period T = 
6. It is desired to pass only 10% of the current through a galvanometer of resistance 90
. How much shunt resistance be connected across the galvanometer?
Ans. IG = 10% of I = 
S = 
S = 
S = 
=> 