Tag: electromagnetic induction

Quizzes (6) Questions (197)

Questions Related to electromagnetic induction

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

Which of the following does not have the same dimensions as the Henry?

  1. $\dfrac{\text {joule}}{(\text{ampere})^2}$
  2. $\dfrac{\text {tesla} - m^2}{(\text{ampere})^2}$
  3. $\text{ohm-second}$
  4. $\dfrac{1}{\text{Farad-second}}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Option $D$ is does not have the same dimensions as the Henry.

So, Option $D$ is correct.

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

Alternating current is flowing in inductance L and resistance R. The frequency of source is $\displaystyle\frac{\omega}{2\pi}$. Which of the following statement is correct.

  1. For low frequency the limiting value of impedance is L
  2. For high frequency the limiting value of impedance is $L\omega$

  3. For high frequency the limiting value of impedance is R
  4. For low frequency the limiting value of impedance is $L\omega$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$\begin{array}{l} \, \, As\, frequency\, approaches\, zero\, or\, DC,\, the\, inducators\, reac\tan  ce\, would\, decrease\, tozero\, , \ acting\, like\, a\, short\, circuit.\, this\, means\, inductive\, reac\tan  ce\, is\, proportional\, to\, fequency \ \, \, \, \, \, \, \, \, \, \, \, \, \, so\, ,\, for\, low\, frequency\, the\, { { limimiting } }\, \, value\, of\, impedance\, is\, L,\, and\, \, alternating\,  \ current\, is\, flowing\, in\, inductance\, L\, and\, resistance\, R.\, \, The\, frequency\, of\, source\, is\, \frac { \omega  }{ { 2\pi  } } . \ so\, the\, correct\, option\, is\, A. \end{array}$

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

A student measures the terminal potential difference (V) of a cell (of emf $\varepsilon$ and internal) resistance r) as a function of the current (I) flowing through it. The slope and intercept of the graph between V and I, then respectively equal to :



  1. $-\in \;and\;r$
  2. $\in \;and\;-r$
  3. $-r\;and\;\in \;$
  4. $r\;and\;-\in$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$E = V + Ir $
$\Rightarrow V=E-Ir$ 
$Comparing\;with\; y = mx + c$ 
$Slope = - r, intercept = E$




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

If circular coil with $N _{1}$ turns is changed in to a coil of $N _{2}$ turns. What will be the ratio of self inductances in both cases.

  1. $\dfrac {N _{1}}{N _{2}}$
  2. $\dfrac {N _{2}}{N _{1}}$
  3. $\dfrac {N _{1}^{2}}{N _{2}^{2}}$
  4. $\sqrt {\dfrac {N _{1}}{N _{2}}}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If circular coil with N1 turns is changed in to a coil of N2 turns. 

$L=\dfrac{Nd \phi}{dt} $
$L _1=\dfrac{N _1d \phi}{dt} $
$L _2=\dfrac{N _2d \phi}{dt} $ 
 L is in Henries
        N is the Number of Turns
        Φ is the Magnetic Flux
        Ι  is in Amperes
$\dfrac{L _1}{L _2}=\dfrac{N _1}{N _2} $
Multiple choice introduction to induction electromagnetic induction electromagnetic induction and alternating currents physics

If the number of turns per unit length of a coil of a solenoid is doubled the self-inductance of the solenoid will:

  1. remain unchanged

  2. be halved

  3. be doubled

  4. become four times
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The self-inductance of a solenoid is proportional to the square of the number of turns per unit length (L is proportional to n^2). If n is doubled, L becomes 2^2 = 4 times the original value.

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

Henry, the SI unit of inductance can be written as :

  1. weber ampere$^{-1}$
  2. volt second ampere$^{-1}$
  3. joule ampere$^{-1}$
  4. ohm s$^{-1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The SI unit of inductance is Henry,
$\displaystyle L =-\dfrac{e}{\dfrac{di}{dt}}$
SI unit $= \displaystyle \dfrac{volt}{A} \times s$
$=volt \times second \times  ampere^{-1}$

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

Multiple Correct Answers Type
The SI unit of inductance, henry, can be written as

  1. Weber/ampere

  2. Volt-second / ampere
  3. $Joule / (ampere)^2$

  4. Ohm-second
Reveal answer Fill a bubble to check yourself
A,B,C,D Correct answer
Explanation

$L=\cfrac{\phi}{i}$

$L=\cfrac{weber}{Ampere}$
$V=L\cfrac{Ldi}{dt}$
$L\to$ volt.second/ampere
$E=\cfrac{1}{2}Li^2$
$L\to $joule/(ampere$)^2$
$\omega L=X _L$
$L\to$ohm.second
Hence all are correct.

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

A lossless coaxial cable has a capacitance of $7\times { 10 }^{ -11 }$ F and an inductance of $0.39\mu H$. Calculate characteristic impedance of the cable.

  1. 65

  2. 75

  3. 66

  4. 77
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Here,$C=7\times { 10 }^{ -11 }F$,
        $L=0.39\times { 10 }^{ -6 }H$

         ${ Z } _{ o }$ As the cable is lossless,
        $\therefore { Z } _{ o }\sqrt { \dfrac { L }{ C }  } =\sqrt { \dfrac { 0.39\times { 10 }^{ -6 } }{ 7\times { 10 }^{ -11 } }  } =75ohm$

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

A source of 220 V is applied in an A C circuit . The value of resistance is 220 $\Omega$. Frequency & inductance are 50Hz & 0.7 H then wattless current is 

  1. 0.5 amp

  2. 0.7 amp

  3. 1.0 amp

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A source= $220V$

The value of resistance= $220 \Omega$
Frequency= $50 Hz$
Inductance= $0.7H$
Find the wattless current= ?
Wattless component of current is $i=i _v\sin \theta$
                                                            $=\cfrac {Ev}{z}\sin \theta$
where, $z=$ impedance of $L-R$ circuit
                $=\sqrt {R^2+L^2W^2}$ so,
$i=\cfrac {220}{\sqrt {R^2+L^2+W^2}}\sin \theta$ from impedance triangle,
$\sin \theta= \cfrac {LW}{\sqrt {R^2+L^2W^2}}$
$\Rightarrow i=\cfrac {220}{\sqrt {R^2+L^2W^2}}\cfrac {LW}{\sqrt {R^2+L^2W^2}}$
        $=\cfrac {220}{R^2+L^2W^2}LW$
        $=\cfrac {220 \times 0.7 \times 2 \Pi \times 50}{(220)^2+(0.7\times 2\Pi \times 50)^2}$
        $=\cfrac {220 \times 220}{(220)^2+(220)^2}$
        $=0.5 A$ .