AIIMS Physics Electromagnetic Waves Class 12 Questions

For a toroid N = 500, radius = 40 cm, and area of cross section = 10 cm². Find inductance.

The number of turns is inversely proportional to the current. Nₚ/Nₛ = iₛ/iₚ. 140/280 = iₛ/4. iₛ = 2 Å

If maximum energy is stored in capacitor at t = 0 then find the time after which current in the circuit will be maximum.

The expression of force is given by, 𝐹⃗ = 𝑄𝐸⃗ +𝑄(𝑉⃗ ×𝐵⃗ ) = (1.6×10⁻¹⁹) [(10𝑖̂×10⁻⁶) + (1.6×10⁻¹⁹) [(2𝑖̂) × (𝑖̂ + 3𝑗̂ + 4𝑘̂)] × 10⁻⁹ = (1.6×10⁻¹⁹) [10𝑖̂ − 8𝑗̂ + 6𝑘̂] × 10⁻⁶ N Calculate the acceleration as follows, 𝑎⃗ = (1.6×10⁻¹⁹) [10𝑖̂ − 8𝑗̂ + 6𝑘̂] × 10⁻⁶ N / 1.6×10⁻²⁷ = 1400 m/s²

Consider the phasor diagram for an LCR circuit.

Ratio of electric and magnetic field due of moving point charge if its speed is 4.5×10⁵ m/s

In toroid magnetic field on axis will be the radius = 0.5 cm, current = 1.5A, turns = 250, permeability = 700.

The expression to calculate the induced magnetic field is given as,

Assertion: For communication antenna length should be comparable to λ. (ℓ ∼ λ) Reason: It leads to maximum power

Assertion: If a charged particle is released from rest in a region of uniform electric and magnetic fields parallel to each other, it will move in a straight line. Reason: The electric field exerts no force on the particle but the magnetic field does.

The expression to calculate the electric flux is given by, ϕ = NBA Substitute the values in the above equation. LI = N·(μ₀I/2a)×πa²·N Here, N×2πa = l N = l/2πa Substitute the value of N. LI = (l/2πa)·(μ₀I/2a)×πa²·(l/2πa) L ∝ a⁻¹

The expression of self inductance is given as, L = μ₀μᵣn²Aℓ Here, n = N/ℓ So, L = μ₀μᵣ(N/ℓ)²Aℓ L = μ₀μᵣN²A/ℓ

The common antenna is a straight conductor of length L = λ/4 held vertically with its lower end touching the ground.

In terms of basic units of mass (M), length (L), time (T) and charge (Q), the dimensions of magnetic permeability of vacuum (μ₀) would be

In a series RC circuit having battery of 12 V, capacitor is charged from 0 to 6 V in 0.1 s. Find value of resistance R.

The charge on the capacitor when the energy is stored equally between the electric and magnetic field is calculated as, q²/2C = 1/2 Q²/2C, q = Q/√2

A wire having mass m and length l can freely slide on a pair of parallel smooth horizontal rails placed in vertical magnetic field B. The rails are connected by a capacitor of capacitance C. The electric resistance of the rails and the wire is zero. If a constant force F acts on the wire as shown in the figure. Then, the acceleration of the wire can be given as

Find the average energy density corresponding to maximum electric field, if magnetic field in a plane electromagnetic wave is given by B = 200 × 10⁻⁶ sin[(4 × 10¹⁵)(t − x/c)]

The self inductance of the coil is directly proportional to the square of number of turns in a coil. It is given as L ∝ N².

The expression of frequency is, v = \( \frac{qB}{2\pi m} \) From above expression, it can be concluded that, the assertion is incorrect.

Assertion: The velocity of electromagnetic waves depends on electric and magnetic properties of the medium. Reason: Velocity of electromagnetic waves in free space is constant.

Assertion: Cyclotron does not accelerate electron. Reason: Mass of the electron is very small.

Assertion: The electromagnetic waves are transverse in nature. Reason: Waves of wavelength 10 μm are radiowave and microwave.

Assertion: When a charge particle moves in a circular path. It produces electromagnetic wave. Reason: Charged particle has acceleration.

Assertion (A) A charge moving in a circular orbit can produce electromagnetic wave. Reason (R): The source of an electromagnetic wave should be in accelerated motion.

Which of the following is the best method to reduce eddy currents?

Two solenoids of equal number of turns having their length and the radii in the same ratio 1 : 2. The ratio of their self-inductance will be

Assertion: Electromagnetic radiations exert pressure. Reason: Electromagnetic-waves carry both momentum and energy.

The frequency order for X⁻rays (A), γ-rays (B), UV rays (C) is

Assertion: In electromagnetic waves electric field and magnetic field lines are perpendicular to each other. Reason: Electric field and magnetic field are self sustaining.

Magnetic energy per unit volume is represented by

Assertion: An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube. Reason: Electric field requires low voltage.

Assertion: Electromagnetic waves are transverse in nature. Reason: The electric and magnetic fields of an e.m. wave are perpendicular to each other and also perpendicular to the direction of wave propagation.

Light with an energy flux of 18 W/cm² falls on a non-reflecting surface at normal incidence. The pressure exerted on the surface is

A coil of wire of a certain radius has 100 turns and a self inductance of 15 mH. The self inductance of a second similar coil of 500 turns will be

If v₁, v₂ and v₃ are the speeds of gamma rays, X⁻rays and microwaves respectively in vacuum, then

Assertion : Transformers are used only in alternating current source not in direct current. Reason : Only a.c. can be stepped up or down by means of transformers.

Assertion : The dimensional formula for product of resistance and conductance is same as for dielectric constant. Reason : Both have dimensions of time constant.

In an electrical circuit containing L, C and R which of the following does not denote the dimensions of frequency?

The velocity of electromagnetic radiation in a medium of permittivity ε₀ and permeability μ₀ is given by

Assertion: The alternating current lags behind the e.m.f. by a phase angle of π/2, when AC flows through an inductor. Reason: The inductive reactance increases as the frequency of AC source decreases.

Assertion: A spark occur between the poles of a switch when the switch is opened. Reason: Current flowing in the conductor produces magnetic field.

Assertion: Inductance coils are usually made of thick copper wire. Reason: Induced current is more in wire having less resistance.

In the following diagram, which particle has highest e/m value?

What is the dimensions of impedance ?

Assertion : Dipole oscillations produce electromagnetic waves. Reason : Accelerated charge produces electromagnetic waves.

Assertion : Electromagnetic waves with frequencies smaller than the critical frequency of ionosphere cannot be used for communication using sky wave propagation. Reason : The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency.

Assertion : An emf E is induced in a closed loop where magnetic flux is varied. The induced E is not a conservative field. Reason : The line integral E⋅dl around the closed loop is non-zero.

The pressure exerted by an electromagnetic wave of intensity I (watt/m²) on a nonreflecting surface is [c is the velocity of light]

Assertion : Television signals are received through sky-wave propagation. Reason : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.