Electromagnetic Induction — NEET UG practice

32 questions

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Sample questions with solutions

Q1 · 2026

Two identical inductors are connected in two different configurations PP and QQ, where a time varying current I(t)I(t) is flowing, as shown in the figure. The induced emf between points aa and bb for configuration PP is EPE_P and that for configuration QQ is EQE_Q. The ratio EP/EQE_P/E_Q is:

[Neglect the effect of mutual inductance.]

  • A.

    22

  • B.

    14\frac{1}{4}

  • C.

    12\frac{1}{2}

  • D.

    11

Answer: A
  1. For any inductor, the induced emf opposes the change in current and is given by: ε=LdIdt\varepsilon = -L\frac{dI}{dt}

  2. In configuration PP, the two identical inductors combine to give an effective inductance LL across aa and bb. So: EP=LdI(t)dtE_P = -L\frac{dI(t)}{dt}

  3. In configuration QQ, the way the two inductors are connected gives an effective inductance of L/2L/2. So: EQ=L2dI(t)dtE_Q = -\frac{L}{2}\frac{dI(t)}{dt}

  4. Dividing the two expressions to compare them: EPEQ=LL/2=2\frac{E_P}{E_Q} = \frac{L}{L/2} = 2

Hence, the answer is option A.

Q2 · 2026

A conducting loop of finite resistance lies on the xyx-y plane. There is a constant magnetic field in the zz direction. The area of the loop varies with time tt, as A=A0(1+sint)A=A_0(1+\sin t) in appropriate units. The figure that correctly indicates the qualitative behaviour of the power PP dissipated in the loop as a function of time is:

  • A.

  • B.

  • C.

  • D.

Answer: C
  1. The area of the loop is given as: A=A0(1+sint)A = A_0(1+\sin t)

  2. Faraday's law states the induced emf equals the negative rate of change of magnetic flux, and since ϕ=BA\phi = BA: ε=dϕdt=BA0cost\varepsilon = -\frac{d\phi}{dt} = -BA_0\cos t

  3. By Ohm's law, the induced current in the loop is: I=εR=BA0RcostI = \frac{\varepsilon}{R} = -\frac{BA_0}{R}\cos t

  4. Power dissipated in a resistor is P=I2RP = I^2R. Substituting the current: P=B2A02Rcos2tP = \frac{B^2A_0^2}{R}\cos^2 t

  5. So Pcos2tP \propto \cos^2 t, which is always non-negative and oscillates with twice the frequency of sint\sin t.

Hence, the correctly matching graph is option C.

Q3 · 2026

A rectangular wire loop of sides 8 cm and 3 cm with a small cut, is moving out of a region of uniform magnetic field of magnitude 0.3 T directed normal to the plane of the loop. The emf developed across the cut, if the velocity of the loop is 2 cm s12\text{ cm s}^{-1}, in a direction normal to the shorter side of the loop, will be :

  • A.

    4.8×1044.8\times10^{-4} volt

  • B.

    1.2×1041.2\times10^{-4} volt

  • C.

    1.3×1041.3\times10^{-4} volt

  • D.

    1.8×1041.8\times10^{-4} volt

Answer: D
  1. When a conducting rod of length ll moves with velocity vv perpendicular to a magnetic field BB, the motional emf induced across it is: ε=Bvl\varepsilon = Bvl

  2. Here the loop moves in a direction normal to the shorter side, so the emf is induced across that shorter side, l=3 cml = 3\text{ cm}, with v=2 cm/sv = 2\text{ cm/s} and B=0.3 TB = 0.3\text{ T}. Converting to SI units and substituting: ε=0.3×(2×102)×(3×102)\varepsilon = 0.3 \times (2\times10^{-2}) \times (3\times10^{-2})

  3. Calculating the product: ε=1.8×104 V\varepsilon = 1.8\times10^{-4}\text{ V}

Hence, the answer is option D.

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