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Rajasthan Board Class 12 (RBSE) Magnetism & EMI — practice questions

Explore 29 free Magnetism & EMI questions in Rajasthan Board Class 12 (RBSE) Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Magnetism & EMI questions and exercises with answers

Showing questions 1–29 of 29.

A $50$-turn coil has a magnetic flux changing through it at a uniform rate of $4 \times 10^{-3}\,\text{Wb/s}$. The induced EMF in the coil is:Read the answer and worked solution →Lenz's law is a direct consequence of:Read the answer and worked solution →The SI unit Henry (H) is equivalent to:Read the answer and worked solution →The self-inductance of a long air-cored solenoid of length $\ell$, cross-sectional area $A$ and total number of turns $N$ is:Read the answer and worked solution →The energy stored in an inductor of inductance $L$ carrying a steady current $I$ is:Read the answer and worked solution →An ideal LC circuit oscillates freely. If $L = 4\,\text{mH}$ and $C = 25\,\mu\text{F}$, the angular frequency of oscillation is:Read the answer and worked solution →The Lorentz forceRead the answer and worked solution →Work done by a magnetic forceRead the answer and worked solution →Reading the Lorentz forceRead the answer and worked solution →Force on a current wireRead the answer and worked solution →The current carrying conductorRead the answer and worked solution →Charge in a uniform fieldRead the answer and worked solution →What the cyclotron frequency ignoresRead the answer and worked solution →The cyclotron machineRead the answer and worked solution →Formula to what it describesRead the answer and worked solution →The Biot-Savart lawRead the answer and worked solution →Using Biot-SavartRead the answer and worked solution →Field of a circular coilRead the answer and worked solution →Odd one out: magnetismRead the answer and worked solution →Depends on speed or notRead the answer and worked solution →True of the magnetic forceRead the answer and worked solution →Symbol to quantityRead the answer and worked solution →Which is largerRead the answer and worked solution →Field and force directionsRead the answer and worked solution →Currents make fieldsRead the answer and worked solution →Count and computeRead the answer and worked solution →Odd one out: what a current doesRead the answer and worked solution →Zero work, changing directionRead the answer and worked solution →Moving charges, mixed checkRead the answer and worked solution →

Worked practice questions

A $50$-turn coil has a magnetic flux changing through it at a uniform rate of $4 \times 10^{-3}\,\text{Wb/s}$. The induced EMF in the coil is:

  1. $1.00\,\text{V}$
  2. $0.20\,\text{V}$
  3. $0.05\,\text{V}$
  4. $0.10\,\text{V}$
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Correct answer: B. $0.20\,\text{V}$

Faraday's law: $|\varepsilon| = N \dfrac{d\Phi}{dt} = 50 \times 4 \times 10^{-3} = 0.20\,\text{V}$.

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Lenz's law is a direct consequence of:

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

If the induced current did not oppose the change in flux, the system would gain energy without any external work being done, creating a perpetual-motion situation. The negative sign in $\varepsilon = -d\Phi/dt$ enforces conservation of energy by ensuring that work has to be done against the induced effects.

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The SI unit Henry (H) is equivalent to:

  1. $\text{Wb}\cdot\text{A}$
  2. $\text{V}\cdot\text{s}\cdot\text{A}^{-1}$
  3. $\text{T}\cdot\text{m}^2$
  4. $\text{V}\cdot\text{A}^{-1}$
Show answer and solution

Correct answer: B. $\text{V}\cdot\text{s}\cdot\text{A}^{-1}$

From $\varepsilon = -L \dfrac{dI}{dt}$, $L$ has units of $\text{V}/(\text{A/s}) = \text{V}\cdot\text{s}\cdot\text{A}^{-1}$. This is the same as $\text{Wb}/\text{A}$ since $1\,\text{Wb} = 1\,\text{V}\cdot\text{s}$.

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