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CG PET Electromagnetic Induction — practice questions

Explore 53 free Electromagnetic Induction questions in CG PET Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Electromagnetic Induction questions and exercises with answers

Showing questions 1–30 of 53.

Faraday's law of electromagnetic induction (in its quantitative form, with sign) is:Read the answer and worked solution →Lenz's law is a manifestation of which fundamental conservation principle?Read the answer and worked solution →The motional EMF induced in a conductor of length $\ell$ moving with velocity $v$ perpendicular to a uniform magnetic field $B$ is:Read the answer and worked solution →The SI unit of magnetic flux is:Read the answer and worked solution →The SI unit of self-inductance $L$ is:Read the answer and worked solution →The induced EMF in a coil due to changing current in itself is given by:Read the answer and worked solution →The energy stored in an inductor of inductance $L$ carrying current $I$ is:Read the answer and worked solution →Mutual inductance $M$ between two coils satisfies:Read the answer and worked solution →The energy density (energy per unit volume) of a magnetic field $B$ in free space is:Read the answer and worked solution →A conducting rod of length 1 m moves with velocity 5 m/s perpendicular to a uniform magnetic field of 0.4 T. The motional EMF is:Read the answer and worked solution →The self-inductance of a long solenoid with $n$ turns per unit length, cross-section $A$ and length $\ell$ is:Read the answer and worked solution →A solenoid of $N = 200$ turns, length $L = 20$ cm and cross-section $A = 5\ \text{cm}^2$ has self-inductance approximately:Read the answer and worked solution →A current of 4 mA in a coil of self-inductance 10 mH and 200 turns produces total flux:Read the answer and worked solution →When two inductors $L_1$ and $L_2$ are connected in **series** (no mutual inductance), the equivalent inductance is:Read the answer and worked solution →Two inductors of 4 H and 12 H are connected in **parallel** (no mutual inductance). The equivalent inductance is:Read the answer and worked solution →If the current in a coil of inductance 5 H changes from 2 A to 5 A in 0.1 s, the magnitude of induced EMF is:Read the answer and worked solution →If the current in a primary coil changes at 30 A/s and induces 0.6 V in a secondary coil, the mutual inductance is:Read the answer and worked solution →The energy stored per unit volume in a magnetic field $B = 0.1$ T in vacuum (take $\mu_0 = 4\pi \times 10^{-7}$ N/A²) is approximately:Read the answer and worked solution →A coil of self-inductance 2 H carries a current of 4 A. The energy stored in its magnetic field is:Read the answer and worked solution →Faraday's law of electromagnetic induction states EMF induced equals:Read the answer and worked solution →Lenz's law states the induced current direction is such that it:Read the answer and worked solution →SI unit of magnetic flux is:Read the answer and worked solution →Mutual inductance M between two coils is defined by EMF induced in coil 2:Read the answer and worked solution →Self-inductance L of a coil relates EMF to:Read the answer and worked solution →Energy stored in an inductor of inductance L carrying current I:Read the answer and worked solution →Magnetic flux Φ = B A cos θ. If a coil of area 0.1 m² in B = 0.5 T is rotated from θ=0° to θ=60° in 0.2 s, average EMF:Read the answer and worked solution →A rod of length L moves with velocity v perpendicular to magnetic field B. Motional EMF:Read the answer and worked solution →In a transformer with N₁ = 100 (primary), N₂ = 500 (secondary), if input is 10 V, output is:Read the answer and worked solution →In LR circuit, time constant τ:Read the answer and worked solution →For an ideal inductor in AC circuit at angular frequency ω, inductive reactance:Read the answer and worked solution →

Worked practice questions

Faraday's law of electromagnetic induction (in its quantitative form, with sign) is:

  1. $e = \phi / t$
  2. $e = \phi \cdot dt$
  3. $e = -d\phi/dt$
  4. $e = +d\phi/dt$
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Correct answer: C. $e = -d\phi/dt$

The induced EMF equals the **negative** rate of change of magnetic flux through the circuit: $e = -d\phi/dt$. The minus sign embeds Lenz's law — direction of induced EMF opposes the flux change.

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Lenz's law is a manifestation of which fundamental conservation principle?

  1. Conservation of energy
  2. Conservation of mass
  3. Conservation of momentum
  4. Conservation of charge
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Correct answer: A. Conservation of energy

If induced current aided the flux change, it would self-sustain and grow indefinitely — producing energy from nothing. **So the opposing direction is forced by energy conservation.**

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The motional EMF induced in a conductor of length $\ell$ moving with velocity $v$ perpendicular to a uniform magnetic field $B$ is:

  1. $Bv/\ell$
  2. $B\ell v$
  3. $B/(\ell v)$
  4. $B\ell/v$
Show answer and solution

Correct answer: B. $B\ell v$

When a straight conductor of length $\ell$ moves perpendicular to $B$ with speed $v$, the rate of flux change is $B\ell v$, so $|e| = B\ell v$.

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