Download full question paper on magnetic effect of current

CLASS - XII PHYSICS (Unit –Magnetic effects of current)
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A cyclotron is not suitable to accelerate electron. Why?
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Can neutrons be accelerated in a cyclotron. Why?
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Which physical quantity has the unit wb/m2. Is it a scalar or vector quantity?
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State Ampere’s circuital law. Write the expression for the magnetic field at the centre of
a circular coil of readius R carrying a current l. Draw the magnetic field lines due to this
coil.
Write the expression for the force acting on a charged particle of charge q moving with
⃗⃗. Show that in the presence of this force:
velocity 𝑣⃗ in the presence of magnetic field 𝐵
(i)
(ii)
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the kinetic energy of th particle does not change
its instantaneous power is zero.
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A circular coil of 200 turns and radius 10 cm is placed in a uniform magnetic field of 0.5
T, normal to the plane of the coil. If the current in the coil is 3.0 A, calculate the
(a) total torque on the coil
(b) total force on the coil.
(c) Average force on each electron in the coil, due to the magnetic field.
Assume the area of cross-section of the wire to be 10-5m2 and the free electron density
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is 1029/m3.
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Deduce the expression for the torque experienced by a rectangular loop carrying a
⃗⃗. Indicate the direction of the
steady current ‘l’ and placed in a uniform magnetic field 𝐵
torque acting on the loop.
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Depict the field-line pattern due to a current carrying solenoid of finite length.
(i)
(ii)
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In what way do these lines differ from those due to an electric dipole?
Why can’t two magnetic field lines intersect each other?
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A rectangular loop of wire of size 4 cm X 10 cm carries a steady current of 2 A. A
straight long wire carrying 5 A current is kept near the loop as shown. If the loop and
the wire are coplanar find (i) the torque acting on the loop and (ii) the magnitude and
direction of the force on the loop due to the current carrying wire.
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Draw a labeled diagram of a moving coil galvanometer and explain its working. What is
the function of radial magnetic field inside the coil?
Sandeep’s mother had put lot of clothes for washing in the washing machine, but the
machine did not start and an indicator was showing that the lid did not close. Sandeep
seeing his mother disturbed thought that he would close the lid by force but realized
the mechanism was different. It was a magnetic system. He went to the shop and got
a small magnetic door closer and put it on the lid. The machine started working. His
mother was happy that Sandeep helped her to save Rs. 500/- also.
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What was the value developed by Sandeep?
What values did his mother impart to Sandeep?
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(a) Derive an expression for the force per unit length experienced by two infinitely
long straight parallel wires, carrying currents in the same direction.
(b) (i) use the above to define one ampere
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(ii) show that the oppositely directed parallel currents repel whereas currents
flowing in the same direction attract.
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(a) Write the expression for the force, 𝐹⃗ , acting on a charged particle of charge ‘q’,
⃗⃗ in the presence of both electric field 𝐸⃗⃗ and magnetic
moving with a velocity 𝑉
⃗⃗. Obtain the condition under which the particle moves undeflected
field 𝐵
through the fields.
(b) A rectangular loop of size l x b carrying a steady current is placed in a uniform
⃗⃗. Prove that the torque 𝑡⃗ acting on the loop is given by 𝑡⃗ =𝑚
magnetic field 𝐵
⃗⃗⃗ x 𝑏⃗⃗
where 𝑚
⃗⃗⃗ is the magnetic movement of the loop.
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