Tag: properties of magnet

Questions Related to properties of magnet

A particle of charge $q$ and mass $m$ starts moving from origin under the action of an electric field $\vec { E }$=$E _ { 0 } \vec i $ and magnetic field $\vec { B }$=$B _ { 0 } \vec k $ . Its  velocity at $( x , 3,0 )$ is $( 4 i + 3 i )$ , the value of $x$ is:

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. $\dfrac { 36 E _ { o } B _ { 0 } } { q m }$

  2. $\dfrac { 25 m } { 2 q E _ { 0 } }$

  3. $\dfrac { 10 m } { q E _ { o } }$

  4. $\dfrac { 25 E _ { 0 } B _ { 0 } } { m }$

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Correct Option: B
Explanation:

$\begin{array}{l} \left( { q{ \varepsilon _{ 0 } } } \right) x=\frac { 1 }{ 2 } m{ v^{ 2 } } \ \Rightarrow q{ \varepsilon _{ 0 } }x=\frac { { 25m } }{ 2 }  \ x=\frac { { 25 } }{ { 2q{ \varepsilon _{ 0 } } } }  \ Hence, \ option\, \, B\, \, is\, \, correct\, \, answer. \end{array}$

Pick correct statements from among the following : 
a) Electric field and magnetic field are basically independent
b) Electric field and magnetic field are to aspects of the electromagnetic field
c) Electric field and magnetic field may be produced by charge at rest
d) A moving charge produces both electric and magnetic fields

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. a and b are correct

  2. b and d are correct

  3. b, c and d are correct

  4. a, c and d are correct

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Correct Option: B
Explanation:

Electric field and magnetic field are not independent. They are two aspects of the electromagnetic field. Charge at rest only produces electric field. Moving charge produces both electric field and magnetic field.

Two particles having the same specific change (q/m) enter a uniform magnetic field with the same speed but at angles of $30^ \circ$ and $60^\circ$ with the field. Let a, b and c be the ratios of their pitches, radii and periods of their helical paths respectively, then

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. $abc = 1$

  2. $a + b = 2 \sqrt c$

  3. $a^2 = c$

  4. $ab = c$

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Correct Option: D

In a given region a charge particle is moving under the effect of electric and magnetic field with uniform velocity $\vec{v}=(\hat{i}+\hat{j}-\hat{k})$ m/s and magnetic field is given as $\vec{B}=(2\hat{i}+\hat{j}-2k)T$. The electric field is given as?

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. $({i}+{j}-{k})$ V/m

  2. $({i}-{j}+{k})$ V/m

  3. $({i}+k)$ V/m

  4. $(-{i}-{k})$ V/m

Show answer
Correct Option: D
Explanation:

We know Force $F=qE$------(1)

and also $F=qV\times B$-----(2)
From 1 and 2 we get 
$V\times B=E$
$V\times B$=\begin{matrix} \hat { i }  & \hat { j }  & \hat { i }  \ 1 & 1 & -1 \ 2 & 1 & -2 \end{matrix}
$V\times B=(-2+1)\hat { i } -(-2+2)\hat { j } +(1-2)\hat { k } $
$V\times B==-\hat { i } -\hat { k } $

A long, straight, $non-$ conducting string, painted with a charge density of $40\mu\ c/m$, is pulled along its length at a speed of $300\ m/s$. The magnetic field at a normal distance of $5\ mm$ from the moving string is $4.8\times {10}^{-1}\ T$

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. $4.8\times {10}^{-1}\ T$

  2. Zero

  3. $\infty$

  4. Cannot be found

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Correct Option: A

 Two concentric circular coils of $10$ turns each are situated in the same plane. Their radii are $20$ cm and $40$ cm and carry currents of $0.2$ A and $0.3$ A respectively in opposite directions. The net magnetic induction field at their common centre is 

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. $\cfrac {35\mu _0}{4}$

  2. $\cfrac {5\mu _0}{4}$

  3. $\cfrac {7\mu _0}{8}$

  4. $\cfrac {\mu _0}{80}$

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Correct Option: B

A coil having resistance $40 \Omega$, number of turns 100 and radius 6 mm is connected to an ammeter of resistance $160 \Omega$. The coil is placed perpendicular to the magnetic field. When the coil is taken out of the field, a charge of $32 \mu C$ passes through it. The intensity of magnetic field will be

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. 6.55 T

  2. 5.66 T

  3. 0.655 T

  4. 0.566 T

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Correct Option: D

In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to other. A charged particle is released from rest in this region. The path of the particle will be a:

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. circle

  2. helix

  3. straight line

  4. ellipse

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Correct Option: A

The magnetic lines of force like electrical lines of force

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. Are closed

  2. Are not closed

  3. Are open

  4. Are not open

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Correct Option: D

Assertion: Basic difference between electric lines and magnetic lines of force is that former are discontinuous and the latter are continuous
Reason: No electric lines of forces exit inside charged conductor but magnetic lines do exist inside magnet

properties of magnet magnetic field moving charges and magnetism magnetic effects of current and magnetism physics

  1. Both A and R are true and R is the correct explanation of A

  2. Both A and R are true and R is not correct explanation of A

  3. A is true, but R is false

  4. A is false, but R is true

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Correct Option: A