Tag: electromagnetic induction and alternating currents

Quizzes (10) Questions (183)

Questions Related to electromagnetic induction and alternating currents

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

if the length and area of cross section of an inductor remain same but the number of turns is doubled its self inductance will become:

  1. half

  2. four time

  3. double

  4. one- fourth
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Self-inductance L is proportional to the square of the total number of turns (N^2). If N is doubled, L becomes 2^2 = 4 times the original.

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

The SI unit of inductance, the 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\dfrac{dI}{dt} = emf = \dfrac{d\phi}{dt}$


a) $ [L] = weber / ampere $

b) $ [L] = volt.second / ampere $

c) $ Joule = volt \times ampere \times second $

$ \Rightarrow volt \times second = Joule / ampere$

$ \Rightarrow [L] = joule/ ampere^2$

d) $ V = IR \Rightarrow volt = ampere.ohm$

$\Rightarrow [L] = ohm.second$.

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

If a spark is produced on removing the load from an AC circuit then the element connected in the circuit is

  1. high resistance

  2. high capacitance

  3. high inductance

  4. high impedance
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

On removal of load from the circuit, the circuit suddenly becomes an open circuit.
Thus $ \dfrac{di}{dt} \rightarrow \infty $
For sparking, high voltage must appear across the open ends. This will happen only in case of an inductor as the voltage drop across the inductor is $ L\dfrac{di}{dt} $
Therefore, the circuit has high inductance.

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

Which of the following units denotes the dimensions ${M}{L}^{2}/{Q}^{2}$, where ${Q}$ denotes the electric charge?

  1. $Weber$ ($Wb$)
  2. $Wb$$/\mathrm{m}^{2}$
  3. $Henry$ ($H$)
  4. $\mathrm{H}/\mathrm{m}^{2}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Weber $=ML^2T^{-2}I^{-1}$
$=ML^2T^{-2}Q^{-1}T=ML^2T^{-1}Q^{-1}$   ($I=QT^{-1}$)
Henry H is  SI unit of inductance. 
$H=ML^2T^{-2}I^{-2}$     also $I=QT^{-1}$
so $H=ML^2T^{-2}Q^{-2}T^2=ML^2Q^{-2}$

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

A magnetic field of $2\times {10}^{-2}T$ acts at right angles to a coil of area $100{cm}^{2}$ with $50$ turns. The average emf induced in the coil is $0.1V$. When it is removed from the field in $t$ second, the value of $t$ is

  1. $10s$
  2. $0.1s$
  3. $0.01s$
  4. $1s$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$e=\cfrac { -\left( { \phi  } _{ 2 }-{ \phi  } _{ 1 } \right)  }{ t } =\cfrac { -\left( 0-NBA \right)  }{ t } =\cfrac { NBA }{ t } $
$ \therefore \quad t=\cfrac { NBA }{ e } =\cfrac { 50\times 2\times { 10 }^{ -2 }\times { 10 }^{ -2 } }{ 0.1 } \quad t=0.1s$