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Magnetism and Magnetic Effects of Electric Current 3 Mark Book Back Question Paper With Answer Key

12th Standard

    Reg.No. :
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Physics

Time : 00:30:00 Hrs
Total Marks : 51

    3 Marks 

    17 x 3 = 51
  1. A short bar magnet has a magnetic moment of 0.5 J T–1. Calculate magnitude and direction of the magnetic field produced by the bar magnet which is kept at a distance of 0.1 m from the centre of the bar magnet along
    (a) axial line of the bar magnet and
    (b) normal bisector of the bar magnet.

  2. Consider a magnetic dipole which on switching ON external magnetic field orient only in two possible ways i.e., one along the direction of the magnetic field (parallel to the field) and another anti-parallel to magnetic field. Compute the energy for the possible orientation.

  3. A coil of a tangent galvanometer of diameter 0.24 m has 100 turns. If the horizontal component of Earth’s magnetic field is 25 x 10–6 T then, calculate the current which gives a deflection of 60o .

  4. Compute the intensity of magnetisation of the bar magnet whose mass, magnetic moment and density are 200 g, 2 A m2 and 8 g cm–3, respectively.

  5. Calculate the magnetic field inside a solenoid, when
    (a) the length of the solenoid becomes twice with fixed number of turns
    (b) both the length of the solenoid and number of turns are doubled
    (c) the number of turns becomes twice for the fixed length of the solenoid.
    Compare the results.

  6. Compute the work done and power delivered by the Lorentz force on the particle of charge q moving with velocity \(\vec { v } \). Calculate the angle between Lorentz force and velocity of the charged particle and also interpret the result.

  7. An electron moving perpendicular to a uniform magnetic field 0.500 T undergoes circular motion of radius 2.50 mm. What is the speed of electron?

  8. A proton moves in a uniform magnetic field of strength 0.500 T magnetic field is directed along the x - axis. At initial time, t  = 0s, the proton has velocity
    \(\hat { v } =(1.95\times { 10 }^{ -5 }\hat { i } +2.00\times { 10 }^{ 5 }\hat { k } )m{ s }^{ -1 }\). Find
    (a) At initial time, what is the acceleration of the proton.
    (b) Is the path circular or helical? If helical, calculate the radius of helical trajectory and also calculate the pitch of the helix (Note: Pitch of the helix is the distance travelled along the helix axis per revolution).

  9. Two singly ionized isotopes of uranium \(_{ 92 }^{ 235 }{ U \ and \ _{ 92 }^{ 238 }{ U } }\) (isotopes have same atomic number but different mass number) are sent with velocity 1.00 x 105 m s–1 into a magnetic field of strength 0.500 T normally. Compute the distance between the two isotopes after they complete a semi-circle. Also, compute the time taken by each isotope to complete one semi-circular path. (Given: masses of the isotopes: m235 = 3.90 x 10–25 kg and m238 = 3.95 x 10–25 kg)

  10. A metallic rod of linear density is 0.25 kg m–1 is lying horizontally on a smooth inclined plane which makes an angle of 45o with the horizontal. The rod is not allowed to slide down by flowing a current through it when a magnetic field of strength 0.25 T is acting on it in the vertical direction. Calculate the electric current flowing in the rod to keep it stationary.

  11. The coil of a moving coil galvanometer has 5 turns and each turn has an effective area of 2 x 10–2 m2. It is suspended in a magnetic field whose strength is 4 x 10–2 Wb m–2. If the torsional constant K of the suspension fibre is 4 x 10–9 N m deg–1.
    (a) Find its current sensitivity in division per microampere.
    (b) Calculate the voltage sensitivity of the galvanometer for it to have full scale deflection of 50 divisions for 25 mV.
    (c) Compute the resistance of the galvanometer

  12. State Biot-Savart’s law.

  13. A bar magnet is placed in a uniform magnetic field whose strength is 0.8 T. If the bar magnet is oriented at an angle 30o with the external field experiences a torque of 0.2 Nm. Calculate
    (i) the magnetic moment of the magnet
    (ii) the work done by the applied force in moving it from most stable configuration to the most unstable configuration and also compute the work done by the applied magnetic field in this case.

  14. A non - conducting sphere has a mass of 100 g and radius 20 cm. A flat compact coil of wire with turns 5 is wrapped tightly around it with each turns concentric with the sphere. This sphere is placed on an inclined plane such that plane of coil is parallel to the inclined plane. A uniform magnetic field of 0.5 T exists in the region in vertically upward direction. Compute the current I required to rest the sphere in equilibrium.

  15. How is a galvanometer converted into (i) an ammeter and (ii) a voltmeter?

  16. Give an account of magnetic Lorentz force.

  17. Calculate the magnetic field at the centre of a square loop which carries a current of 1.5 A, length of each side being 50 cm.

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