Magnetism and Magnetic Effects of Electric Current Book Back Questions

12th Standard EM

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Physics

Time : 00:45:00 Hrs
Total Marks : 30
    5 x 1 = 5
  1. Th e force experienced by a particle having mass m and charge q accelerated through a potential diff erence V when it is kept under perpendicular magnetic field \(\vec { B } \) is

    (a)

    \(\sqrt { \frac { 2{ q }^{ 3 }BV }{ m } } \)

    (b)

    \(\sqrt { \frac { { q }^{ 3 }{ B }^{ 2 }V }{ 2m } } \)

    (c)

    \(\sqrt { \frac { 2{ q }^{ 3 }{ B }^{ 2 }V }{ m } } \)

    (d)

    \(\sqrt { \frac { { 2q }^{ 3 }BV }{ { m }^{ 3 } } } \)

  2. Th ree wires of equal lengths are bent in the form of loops. One of the loops is circle, another is a semi-circle and the third one is a square. Th ey are placed in a uniform magnetic fi eld and same electric current is passed through them. Which of the following loop confi guration will experience greater torque ?

    (a)

    circle

    (b)

    semi-circle

    (c)

    square

    (d)

    all of them

  3. A non-conducting charged ring of charge q, mass m and radius r is rotated with constant angular speed ω. Find the ratio of its magnetic moment with angular momentum is

    (a)

    \(\\ \frac { q }{ m } \)

    (b)

    \(\\ \frac { 2q }{ m } \)

    (c)

    \(\\ \frac { q }{ 2m } \)

    (d)

    \(\\ \frac { q }{ 4m } \)

  4. The vertical component of Earth’s magnetic field at a place is equal to the horizontal component. What is the value of angle of dip at this place?

    (a)

    30° 

    (b)

    45° 

    (c)

    60° 

    (d)

    90° 

  5. A simple pendulum with charged bob is oscillating with time period T and let θ be the angular displacement. If the uniform magnetic field i switched ON in a direction perpendicular to the plane of oscillation then

    (a)

    time period will decrease but θ will remain constant

    (b)

    time period remain constant but θ will decrease

    (c)

    both T and θ will remain the same

    (d)

    both T and θ will decrease

  6. 3 x 2 = 6
  7. State Ampere’s circuital law.

  8. Compare dia, para and ferro-magnetism.

  9. What is meant by hysteresis?

  10. 3 x 3 = 9
  11. The repulsive force between two magnetic poles in air is 9 x 10-3 N. If the two poles are equal in strength and are separated by a distance of 10 cm, calculate the pole strength of each pole.

  12. Two materials X and Y are magnetised, whose intensity of magnetisation are 500
    A m-1 and 2000 A m-1, respectively. If the magnetising field is 1000 A m-1, then which
    one among these materials can be easily magnetized?.

  13. Calculate the magnetic field at a point P which is perpendicular bisector to current carrying straight wire as shown in figure.

  14. 2 x 5 = 10
  15. Show that for a straight conductor, the magnetic field
    \(\overset { \rightarrow }{ B } =\frac { { \mu }_{ ° }I }{ 4\pi a } (cos\varphi _{ 1 }-cos\varphi _{ 2 })\hat { n } \)
    \(=\frac { { \mu }_{ ° }I }{ 4\pi a } (sin{ \theta }_{ 1 }+sin{ \theta }_{ 2 })\hat { n } \)

  16. Let E be the electric field of magnitude 6.0 × 106 N C-1 and B be the magnetic field
    magnitude 0.83 T. Suppose an electron is accelerated with a potential of 200 V, will
    it show zero deflection?. If not, at what potential will it show zero deflection.

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