Tag: electrostatic and magnetic analogy

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Questions Related to electrostatic and magnetic analogy

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

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).

  1. 4$\pi $

  2. 2

  3. 4

  4. 2$\pi $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

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

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

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:

  1. 2.4 N

  2. 1.2 N

  3. 0.6 N

  4. 0.3 N
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

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

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          

  1. mB

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

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

  4. 2mB
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$B=\dfrac{\mu _{0}m}{4\pi d^{2}}$
$r=2d$
$F=\dfrac{\mu _{0}m _{1}m _{2}}{4\pi r^{2}}$
$F=\dfrac{\mu _{0}\times m\times m}{4\pi (d)^{2}}$
$F=\dfrac{\mu _{0}m^{2}}{4\pi \times 4d^{2}}$
$F=\dfrac{mB}{4}N$

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

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)

  1. 1.8, 1.2

  2. 18, 12

  3. 6, 4

  4. 0.6, 3.6
Reveal answer Fill a bubble to check yourself
A Correct answer
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
$0.06\times 10^{-5}=\dfrac{4\pi \times 10^{-7}\times 3m\times 2m}{4\pi \times (0.6)^{2}}$
$m^{2}=(0.6)^{2}$
$m=0.6$
$m _{1}=1.8$
$m _{2}=1.2$