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NCERT Exemplar Class 12 Physics solutions chapter 4 explores the broad prospects of movement of charges giving rise to a study of magnets and magnetism. Daily objects like the permanent magnet on your refrigerator door and the coils of an electric motor in a remote control car, the massive electromagnets used to lift wagons and cars, the magnets used in electron microscopes, and powerful superconducting magnets used in building fusion reactors- the uses of magnetism are vast and diversified. NCERT Exemplar solutions for Class 12 Physics chapter 4 provided on this page would help get a clear and efficient understanding of the academic text and drive one to perform well in the 12 boards and competitive exams. Students can also make use of NCERT Exemplar Class 12 Physics solutions chapter 4 PDF Download for further learning.
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Question:1
Two charged particles traverse identical helical paths in an opposite sense in a uniform magnetic field
a) they have equal z-components of momenta
b) they must have equal charges
c) they necessarily represent a particle-antiparticle pair
d) the charge to mass ratio satisfy:
Answer:
The answer is the option (d) As shown in the diagram if the particle is drawn in x-y plane at an angle of θ and moving with a velocity v, so as to make one component along the field and the other perpendicular, we need to resolve the velocity in rectangular components. After doing so, the particle gains a constant velocity along the field of . And the distance travelled by the particle is known as pitch.Question:2
Biot-Savart law indicates that the moving electrons produce a magnetic field B such that
a)
b)
c) it obeys inverse cube law
d) it is along the line joining the electrons and point of observation
Answer:
The answer is the option (a)Question:3
A current carrying circular loop of radius R is placed in the x-y plane with centre at the origin. Half of the loop with x >0 is now bent so that it now lies in the y-z plane.
(a) The magnitude of magnetic moment now diminishes.
(b) The magnetic moment does not change.
(c) The magnitude ofB at (0,0, z), z>>R increases.
(d) The magnitude ofB at (0,0,z), z>>R is unchanged.
Answer:
The answer is the option (a) According to the right-hand thumb rule, the direction of the magnetic moment of the circular loop is perpendicular to the loop. So, in order to compare their magnetic moments, we need to analyse them in vertical filed.Question:4
An electron is projected with uniform velocity along the axis of a current-carrying long solenoid. Which of the following is true?
a) the electron will be accelerated along the axis
b) the electron path will be circular about the axis
c) the electron will experience a force at 45o to the axis and hence execute a helical path
d) the electron will continue to move with uniform velocity along the axis of the solenoid
Answer:
The answer is the option (d), the electron will continue to move with uniform velocity along the axis of the solenoid.
If the magnetic field of a current-carrying solenoid has a moving electron with uniform velocity across the axis, the electron will face a magnetic force due to magnetic field determined by (in case of F=0, the velocity is parallel to the magnetic field or anti-parallel or ). It will either result in the electron moving with uniform velocity or it will go undeflected across the solenoid axis.
Question:5
In a cyclotron, a charged particle
(a) Undergoes acceleration all the time
(b) speeds up between the dees because of the magnetic field
(c) speeds up in a dee
(d) slows down within a dee and speeds up between dees
Answer:
The answer is the option (a) undergoes acceleration all the time.Question:7
The gyro-magnetic ratio of an electron in an H-atom, according to Bohr model is
a) independent of which orbit it is in
b) negative
c) positive
d) increases with the quantum number n
Answer:
The correct answers are the options (a, b) as according to the Bohr model, the gyro-magnetic ration of an electron in an H-atom is negative and independent of which orbit it is in.Question:8
Consider a wire carrying a steady current, I placed un a uniform magnetic field B perpendicular to its length. Consider the charges inside the wire. It is known that magnetic forces do not work. This implies that
a) motion of charges inside the conductor is unaffected by B since they do not absorb energy
b) some charges inside the wire move to the surface as a result of B
c) if the wire moves under the influence of B, no work is done by the force
d) if the wire moves under the influence of B, no work is done by the magnetic force on the ions, assumed fixed within the wire
Answer:
The correction options are (b, d).Question:9
Two identical current carrying coaxial loops, carry current I in an opposite sense. A simple amperian loop passes through both of them once. Calling the loop as C,
(a)
(b) the value of is independent of sense of C
(c) there may be a point on C where, B and dl are perpendicular
(d) B vanishes everywhere on C
Answer:
The correct answers are the options (b, c).Question:10
A cubical region of space is filled with some uniform electric and magnetic fields. An electron enters the cube across one of its faces with velocity v, and a positron enters via opposite face with velocity -v. At this instant,
(a) the electric forces on both the particles cause identical accelerations.
(b) the magnetic forces on both the particles cause equal accelerations.
(c) both particles gain or lose energy at the same rate.
(d) the motion of the Centre of Mass (CM) is determined by B alone.
Answer:
The correct options are (b, c, d).Question:11
A charged particle would continue to move with a constant velocity in a region wherein,
a)
b)
c)
d)
Answer:
The correct answers are the options (a, b, d).Question:12
Verify that the cyclotron frequency has the correct dimensions of .
Answer:
In the device cyclotron, a circular path is followed by the accelerating particle duet eh magnetic field acting as a centripetal force.Question:13
Show that a force that does no Work must be a velocity-dependent force.
Answer:
To prove that a force with doing no works must be a velocity-dependent force, it is necessary to assume that zero work is done by the force. As given in the following equation:Question:14
Answer:
To reverse the polarity of the dees at the same time as it takes the ion to complete the one-half revolution, the frequency of the voltage va of the applied voltage is changed. This requirement is called resonance condition, shown as va = vcQuestion:16
Answer:
Question:18
Answer:
When a charged particle is moving in both electric and magnetic field, the physical quantities can no help to construct dimensional quantity.Question:19
Answer:
The magnetic force makes a charged particle revolve in a uniform circular motion in the x-y plane, but the electric field increases the speed of the charged particle along the x-direction. This results in increasing the radius of the circular path and so, the moves in a spiral path.Question:20
Answer:
To solve the problem, we need to determine the magnetic field’s direction caused by one wire at the point on other wire, then calculate the magnetic force on the current-carrying wire.Question:21
Answer:
The device named galvanometer can also be used to measure the voltage across a given circuit section just like a voltmeter. To do so, a very high resistance wire is connected to the galvanometer in series. The relation is determined by Ig (G + R) – V in which Ig is galvanometer’s range, G is its resistance and R represents the resistance of the wire connected to the galvanometer in series.Question:22
Answer:
Question:23
Answer:
Question:24
Answer:
To find the net torque it is necessary to calculate the magnetic forces and torques after analysis of the direction of current in both wires.Question:25
Answer:
Due to the presence of the magnetic field B along the x-axis, the momenta of two particles in a circular orbit is in the y-z plane. Assume the momenta of the electron (e– ) and positron (e+) to be p1 and p2, respectively. Both moves in the opposite sense in a circle of radius R. Let p, make an angle θ with the y-axis p2 must make the same angle withy axis.Question:26
Answer:
(i) For equilateral triangle of side a,Question:27
Consider a circular current-carrying loop of radius R in the x-y plane with centre at origin. Consider the line integral
taken along z-axis
(a) Show that monotonically increases with L.
b) Use an appropriate Amperian loop to show that , where I is the current in the wire.
(c) Verify directly the above result.
(d) Suppose we replace the circular coil by a square coil of sides R carrying the same current I. What can you say about and
Answer:
(a) In a circular current-carrying loop in x-y plane, the magnetic field acts along z-axis as shown in below.Question:28
Answer:
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With the widespread use of electricity in modern life, the uses of magnetism increased drastically. NCERT Exemplar Class 12 Physics chapter 4 solutions discuss the use and application of magnetic effect of current. Class 12 Physics NCERT Exemplar solutions chapter 4 also covers the broader aspects of magnetism and includes recording storage for different equipment and storage devices in computers. Even a floppy disk contains a number of tracks which store data digitally. A popular example of digital storage and scanning is the noticeable strip in debit and credit cards. This magnetic strip contains the personal data of the user and could be used for identification purposes, and is often accessed through an ATM.
With so many modern-day applications, magnetism carries the world's workings in its arms and can see several plausible developments and breakthroughs in the future.
· NCERT Exemplar Solutions for Class 12 Physics chapter 4 highlights the interaction of moving charges and the magnetic forces that act on moving charges and current-carrying wires.
· NCERT Exemplar Class 12 Physics solutions chapter 4 will also introduce magnetic forces by using the concept of a field and how a magnetic field gets established by a permanent magnet.
· An in-depth study is included about the magnetic forces and torque exerted on moving charges and currents by magnetic fields, the calculation of the magnetic fields produced by currents and moving charges, the laws to remember, and the properties and applications of magnetism.
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In total 28 questions of NCERT exemplar Class 12 Physics solutions chapter 4 from the main exercise is solved in utmost detail and in the most explanative manner.
Yes, each and every question solved in these solutions is done stepwise, so as to make it easier for the students to understand everything clearly.
For those who want to understand the topic, get help for solving questions and want to prepare for exams, these Class 12 Physics NCERT exemplar solutions chapter 4 can be a great place to start.
The major topic that is covered in this chapter is magnetism and its effects and properties. crucial topics from exam POV are Lorentz force, cyclotron, solenoid, toroid etc.
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hello,
Yes you can appear for the compartment paper again since CBSE gives three chances to a candidate to clear his/her exams so you still have two more attempts. However, you can appear for your improvement paper for all subjects but you cannot appear for the ones in which you have failed.
I hope this was helpful!
Good Luck
Hello dear,
If you was not able to clear 1st compartment and now you giving second compartment so YES, you can go for your improvement exam next year but if a student receives an improvement, they are given the opportunity to retake the boards as a private candidate the following year, but there are some requirements. First, the student must pass all of their subjects; if they received a compartment in any subject, they must then pass the compartment exam before being eligible for the improvement.
As you can registered yourself as private candidate for giving your improvement exam of 12 standard CBSE(Central Board of Secondary Education).For that you have to wait for a whole year which is bit difficult for you.
Positive side of waiting for whole year is you have a whole year to preparing yourself for your examination. You have no distraction or something which may causes your failure in the exams. In whole year you have to stay focused on your 12 standard examination for doing well in it. By this you get a highest marks as a comparison of others.
Believe in Yourself! You can make anything happen
All the very best.
Hello Student,
I appreciate your Interest in education. See the improvement is not restricted to one subject or multiple subjects and we cannot say if improvement in one subject in one year leads to improvement in more subjects in coming year.
You just need to have a revision of all subjects what you have completed in the school. have a revision and practice of subjects and concepts helps you better.
All the best.
Hi,
You just need to give the exams for the concerned two subjects in which you have got RT. There is no need to give exam for all of your subjects, you can just fill the form for the two subjects only.
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