Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Electromagnetic Induction question

2022 · 25 Jun · Shift 1 · Q69
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Physics
  4. /Electromagnetic Induction
  5. /2022 · 25 Jun · Shift 1 · Q69

Electromagnetic Induction question

2022 · 25 Jun · Shift 1 · Q69

JEE MainPhysicsElectromagnetic InductionNumerical+4 / −1
The current in a coil of self inductance 2.0 H is increasing according to I = 2 sin(t2) A. The amount of energy spent during the period when current changes from 0 to 2 A is ‾\underline{\hspace{2cm}}​ J.
Numerical answer
View written solutionFree

Correct answer: 4

  1. Given data
  • Self inductance: L=2.0 HL = 2.0\,\text{H}L=2.0H
  • Current: I=2sin⁡(t2)I = 2\sin(t^2)I=2sin(t2) A

We need the energy spent during the interval in which current changes from 000 to 222 A.


  1. Energy stored in an inductor

The magnetic energy stored in an inductor carrying current III is

U=12LI2U = \frac{1}{2}LI^2U=21​LI2

So, the energy spent in increasing current from I1I_1I1​ to I2I_2I2​ is

ΔU=12L(I22−I12)\Delta U = \frac{1}{2}L\left(I_2^2 - I_1^2\right)ΔU=21​L(I22​−I12​)


  1. Initial and final currents
  • Initial current: I1=0I_1 = 0I1​=0
  • Final current: I2=2 AI_2 = 2\,\text{A}I2​=2A

Thus,

ΔU=12(2)(22−02)\Delta U = \frac{1}{2}(2)\left(2^2 - 0^2\right)ΔU=21​(2)(22−02)

ΔU=1⋅4=4 J\Delta U = 1 \cdot 4 = 4\,\text{J}ΔU=1⋅4=4J


  1. Why the given time dependence is not needed

Although current is given as I=2sin⁡(t2)I = 2\sin(t^2)I=2sin(t2), the energy stored in an ideal inductor depends only on the current value, not on how fast or in what manner it reaches that value.

Hence only the change from 000 A to 222 A matters.


  1. Final answer

4\boxed{4}4​

So, the amount of energy spent is 4 J4\,\text{J}4J.

PreviousNext

More from Electromagnetic Induction

  • In a coil of resistance 8Ω, the magnetic flux due to an external magnetic field varies with time as ϕ=32​(9−t2). The value of total heat produced in the coil, till the flux becomes zero, will be ​J…2022 · Numerical
  • The magnetic flux through a coil perpendicular to its plane is varying according to the relation ϕ=(5t3+4t2+2t−5) Weber. If the resistance of the coil is 5 ohm, then the induced current through the coil at t = 2 s will…2022 · MCQ
  • A 10 Ω, 20 mH coil carrying constant current is connected to a battery of 20 V through a switch. Now after switch is opened current becomes zero in 100 μ s. The average e.m.f. induced in the coil is ​ V.2022 · Numerical
  • Two coils of self inductance L1 and L2 are connected in series combination having mutual inductance of the coils as M. The equivalent self inductance of the combination will be : Includes diagram2022 · MCQ
  • A metallic conductor of length 1 m rotates in a vertical plane parallel to east-west direction about one of its end with angular velocity 5 rad s − 1. If the horizontal component of earth's magnetic field is 0.2 × 10 − 4 T, then…2022 · MCQ
  • A conducting circular loop is placed in X−Y plane in presence of magnetic field B=(3t3j^​+3t2k^) in SI unit. If the radius of the loop is 1 m,…2022 · Numerical
  • A metallic rod of length 20 cm is placed in North-South direction and is moved at a constant speed of 20 m/s towards East. The horizontal component of the Earth's magnetic field at that place is 4 × 10 − 3 T and the angle of dip…2022 · Numerical
  • For the given circuit the current through battery of 6 V just after closing the switch 'S' will be ​ A. Includes diagram2022 · Numerical