Tag: magnetism and matter

Questions Related to magnetism and matter

The susceptibility of a diamagnetic substance is

physics magnetism and matter magnetic materials behaviour of substances in magnetic field classification of magnetic materials

  1. $\infty $

  2. zero

  3. small but negative

  4. small but positive

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Correct Option: C
Explanation:

Diamagnetic sultance
-1 $\leq$ $\chi < 0$ 
$\theta =\mu < 1$
$\chi =susceptibility$

A magnetic pole of pole strength 9.2 A m. is placed in a field of induction 50x10$^{-6}$ Tesla. The force experienced by the pole is :

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 46N

  2. 46$\times$10$^{-4}$N

  3. 4.6$\times$10$^{-4}$N

  4. 460N

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Correct Option: C
Explanation:

$m=9.2Am$
$B=50\times 10^{-6}T$
$F=B\times m$
$F=9.2\times 50\times 10^{-6}$
    $=4.6\times 10^{-4}N$

Two equal poles repel each other with a force of 10$^{-3}$ N. When placed 2cm apart in air, the pole strength of each is (in amp-m).

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 4$\pi $

  2. 2

  3. 4

  4. 2$\pi $

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Correct Option: B
Explanation:

$F=10^{-3}N$
$d=2cm$
$m _{1}=m _{2}=m$
$F=\dfrac{\mu _{0}m _{1}m _{2}}{4\pi d^{2}}$

$10^{-3} = \dfrac{10^{-7}\times m^{2}}{(2\times 10^{-2})^2}$
$m=2Am$

Force between two identical bar magnets whose centres are  $r meters $ apart is $4.8 N,$ when their axis are in the same line. If the separation is increased to $2r$ meters, the force between them is reduced to:

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 2.4 N

  2. 1.2 N

  3. 0.6 N

  4. 0.3 N

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Correct Option: B
Explanation:

$F=\dfrac{\mu _{0}m _{1}m _{2}}{4\pi d^{2}}$
$F\propto \dfrac{1}{d^{2}}$
$Fd^{2}=Constant$
$F _{1}d _{1}^{2}=F _{2}d _{2}^{2}$
$4.8\times r^2=F _{2}(2r)^2$
$F _{2}=1.2  N$

The magnetic induction at a distance d from the magnetic pole of the unknown strength m is B. If an identical pole is now placed at a distance of 2d from the first pole, the force between the two poles is          

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. mB

  2. $\frac{mB}{2}$

  3. $\frac{mB}{4}$

  4. 2mB

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Correct Option: C
Explanation:
$B=\dfrac{\mu _{0}m}{4\pi d^{2}}$
$r=2d$
$F=\dfrac{\mu _{0}m _{1}m _{2}}{4\pi r^{2}}$
$F=\dfrac{\mu _{0}\times m\times m}{4\pi (d)^{2}}$
$F=\dfrac{\mu _{0}m^{2}}{4\pi \times 4d^{2}}$
$F=\dfrac{mB}{4}N$

The force acting on a pole of strength of 20 Am is 8x10$^{-4}$ N, when placed in a magnetic field. The magnetic induction field strength is :

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 4$\times $10$^{-6}$ T

  2. 0.4$\times $10$^{4}$ T

  3. 4 G

  4. 4$\times $10$^{-5}$ T

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Correct Option: D
Explanation:

$m=20Am$
$F=8\times10^{-4}N$
$F=Bm$
$8\times 10^{-4}=20\times B$
$B=4\times 10^{-5}T$

Two magnetic poles have their strengths in the ratio 3 : 2. They are kept at a distance of 0.6 m in air and the force of repulsion is found to be 0.06 dynes. The pole strengths are (in amp. m)

electrostatic and magnetic analogy magnetism and matter magnetic effects of current and magnetism physics

  1. 1.8, 1.2

  2. 18, 12

  3. 6, 4

  4. 0.6, 3.6

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Correct Option: A
Explanation:

$1 dyne = 10^{-5}$
$\mu _{0}=4\pi \times 10^{-7}TmA^{-1}$ 
$m _{1}=3m$
$m _{2}=3m$
$F=\dfrac{\mu _{0}m _{1}\times m _{2}}{4\pi \times r^{2}}$ r=0.6m
$0.06\times 10^{-5}=\dfrac{4\pi \times 10^{-7}\times 3m\times 2m}{4\pi \times (0.6)^{2}}$
$m^{2}=(0.6)^{2}$
$m=0.6$
$m _{1}=1.8$
$m _{2}=1.2$