Tag: electromagnetic induction

Quizzes (6) Questions (197)

Questions Related to electromagnetic induction

Multiple choice physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

The dimensional formula of magnetic flux is ___________.

  1. $\left[ M{ L }^{ 2 }{ T }^{ -2 }{ A }^{ -1 } \right] $
  2. $\left[ M{ L }^{ 2 }{ T }^{ -3 }{ A }^{ -1 } \right] $
  3. $\left[ { M }^{ -1 }{ L }^{ -2 }{ T }^{ 2 }{ A }^{ 1 } \right] $
  4. $\left[ M{ L }^{ 3 }{ T }^{ -2 }{ A }^{ -1 } \right] $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Dimensions of ${ \phi  } _{ B }=$ Unit of $B\times $ Unit of $A$
$=\dfrac { newton }{ ampere-metre } \times { metre }^{ 2 }=\dfrac { newton\times metre }{ ampere } $
$=\dfrac { kg{ ms }^{ -2 }\times m }{ A } =kg{ m }^{ 2 }{ s }^{ -2 }{ A }^{ -1 }=\left[ M{ L }^{ 2 }{ T }^{ -2 }{ A }^{ -1 } \right] $

Multiple choice physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

In an experiment to measure the velocity of electrons, an electric field $(E)$ and a magnetic field $(B)$ are employed to produce zero deflection. Then :

  1. The two fields are parallel and the velocity is given by $BE$
  2. The two fields are perpendicular and the velocity is given by $E/B$
  3. The two fields are parallel and the velocity is given by $E/B$
  4. The two fields are perpendicular and the velocity is given by $BE$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The electric force on electron of charge ${e}$  is,
             $  F= {e}E $ 
                    where, E = electric field.

And Magnetic force ,
            $ F= {e}$ $(V\times B)$
               where, V= velocity of electron in magnetic field
                            B= magnetic field

From the above equations,

          $E= V\times B$
Electric field E is perpendicular to both velocity of electron and the magnetic field. So,  The two field is perpendicular to each other and the velocity of electron is $\dfrac{E}{B}$.

B. The two fields are perpendicular and the velocity is given by $\dfrac{E}{B}$.

Multiple choice physics magnetic fields and electromagnetism magnetic flux density magnetic flux electromagnetic induction

Write the dimensions of Magnetic flux in terms of mass, time, length and charge.

  1. $[M^1L^2T^{-1}Q^{-2}]$
  2. $[M^1L^2T^{-1}Q^{-1}]$
  3. $[M^1L^3T^{-1}Q^{-1}]$
  4. $[M^4L^2T^{-1}Q^{-1}]$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

B. $[M^1 L^2 T^ {-1}Q^{-1}]$


Dimension of magnetic field, 


$[B]=[M^1L^0Q^{-1}]$ 

Dimension of surface Area,

 $[A]=[L^2]$

The magnetic flux , 

$\phi=B.A$

The dimension of magnetic flux in term of mass, time, length and charge,
$[\phi]= [M^1L^2T^{-1}Q^{-1}]$

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

A solenoid coil is wound on a frame of rectangular cross section. If all the linear dimension of the frame are increased by a factor of two and the number of turns per unit length of the coil remains the same, the self-inductance increases by a factor of

  1. $4$
  2. $8$
  3. $12$
  4. $16$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Self inductance, $L = \dfrac{\mu 0 N^2 A}{l}$ _(1)


where N = total number of turns


$n = \dfrac{N}{l}$, where n = number of turns per unit length

$N = nl$ put it in (1)

$L = \dfrac{\mu _0 (n l )^2 A}{l} = \mu _0 n^2 l A$

In the given question n is same
Area will increase by $4$ times
length will increase by $2$ times

$L' = \mu _0 n^2 (2l) (4A) = 8 \mu _0 n^2 lA$

$L' = 8L$ inductance will increased by $8$ times.

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

The unit of inductance is equivalent to

  1. $\dfrac {volt\times ampere}{second}$
  2. $\dfrac { ampere}{volt\times second}$
  3. $\dfrac {volt}{Ampere\times second}$
  4. $\dfrac {volt\times second}{ampere}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$As \, \varepsilon \, = \,  L \, \dfrac{dI}{dt},$
$L \, = \, \varepsilon \dfrac{dt}{dI} \Rightarrow \, L \, = \, \dfrac{volt \times second}{ampere}$

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

Two concentric co-planar circular loops of radii $r _1$ and $r _2$ carry currents of respectively $i _1$ and $i _2$ in opposite directions (one clockwise and the other anticlockwise.) The magnetic induction at the centre of loops is half that due to $i _1$ alone at the centre. If $r _2 = 2r _1$. the value of $i _2 / i _1$ is 

  1. $2$
  2. $\dfrac{1}{2}$
  3. $\dfrac{1}{4}$
  4. $1$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$\begin{array}{l} B=\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } } -\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 2\left( { 2{ r _{ 1 } } } \right)  } }  \ =\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } } -\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 4{ r _{ 2 } } } }  \ { B^{ ' } }=\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } }  \ \Rightarrow B=\frac { { { B^{ ' } } } }{ 2 }  \ \Rightarrow \frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 2{ r _{ 1 } } } } -\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 4{ r _{ 1 } } } } =\frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 4{ r _{ 1 } } } }  \ \Rightarrow \frac { { { \mu _{ o } }{ i _{ 1 } } } }{ { 4{ r _{ 1 } } } } =\frac { { { \mu _{ o } }{ i _{ 2 } } } }{ { 4{ r _{ 1 } } } }  \ \Rightarrow \frac { { { i _{ 1 } } } }{ { { i _{ 2 } } } } =1 \ Hence, \ option\, \, D\, \, is\, \, correct\, \, answer. \end{array}$

Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

When the number of turns in a solenoid is doubled without any change in the length of the solenoid, its self-inductance becomes :

  1. Half

  2. Double

  3. Four times

  4. Eight times
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Self-inductance,
$\begin{array}{l}L \propto {N^2}\\therefore \dfrac{{{L _1}}}{{{L _2}}} = {\left( {\dfrac{{{N _1}}}{{{N _2}}}} \right)^2} = {(2)^2} = 4...........{ since,{N _2} = 2{N _1}} \\left[ {{L _2} = 4{L _1}} \right]\end{array}$