Electromagnetism Questions and Answers

Electromagnetism Questions and Answers

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“Electromagnetism questions and answers” help students and enthusiasts understand key concepts. This post covers 100+ essential electromagnetism Q&A, from basics to advanced topics, aiding exam preparation and conceptual clarity.

Electromagnetism Questions and Answers

Basic Concepts

  1. What is electromagnetism?
  2. Who discovered electromagnetism?
  3. What is the SI unit of electric charge?
  4. Define electric field.
  5. What is magnetic flux?
  6. State Faraday’s law of electromagnetic induction.
  7. What is Lenz’s law?
  8. Define Coulomb’s law.
  9. What is Gauss’s law for electricity?
  10. What is Ampere’s law?

Electricity & Magnetism

  1. How does an electric current produce a magnetic field?
  2. What is the right-hand thumb rule?
  3. What is the difference between electric and magnetic fields?
  4. What is electromagnetic induction?
  5. What is self-inductance?
  6. What is mutual inductance?
  7. What is a solenoid?
  8. What is the principle of an electric motor?
  9. How does a transformer work?
  10. What is eddy current?

Advanced Electromagnetism

  1. What are Maxwell’s equations?
  2. Explain the significance of the Lorentz force.
  3. What is the Poynting vector?
  4. What is displacement current?
  5. What is the skin effect?
  6. What is hysteresis in magnetic materials?
  7. Define permittivity and permeability.
  8. What is the difference between diamagnetic and paramagnetic materials?
  9. What is a ferromagnetic material?
  10. What is electromagnetic radiation?

Applications

  1. How do speakers use electromagnetism?
  2. What is the role of electromagnets in MRI machines?
  3. How do generators produce electricity?
  4. What is the working principle of a relay?
  5. How do wireless chargers work?
  6. What is the use of electromagnets in cranes?
  7. How does an induction cooker work?
  8. What is the principle behind electromagnetic braking?
  9. How do antennas transmit signals?
  10. What is the role of electromagnetism in fiber optics?

Mathematical Problems

  1. Calculate the force between two charges of 2C and 3C separated by 1m.
  2. A wire carries a current of 5A. Find the magnetic field at 0.1m distance.
  3. A solenoid has 1000 turns and a current of 2A. Calculate the magnetic field inside.
  4. A transformer has 200 primary turns and 50 secondary turns. If input voltage is 220V, find output voltage.
  5. A capacitor of 10μF is charged to 100V. Calculate the energy stored.

Answers

  1. Electromagnetism is the study of electric and magnetic fields and their interactions.
  2. Hans Christian Ørsted discovered electromagnetism in 1820.
  3. The SI unit of electric charge is the Coulomb (C).
  4. An electric field is a region around a charged particle where a force is exerted on other charges.
  5. Magnetic flux is the measure of the total magnetic field passing through a given area.
  6. Faraday’s law states that a changing magnetic field induces an electromotive force (EMF).
  7. Lenz’s law states that the direction of induced current opposes the change causing it.
  8. Coulomb’s law states that the force between two charges is proportional to the product of charges and inversely proportional to the square of the distance.
  9. Gauss’s law states that the total electric flux through a closed surface is proportional to the enclosed charge.
  10. Ampere’s law relates the magnetic field around a current-carrying conductor to the current.

Answers (11-45)

Electricity & Magnetism

  1. An electric current produces a magnetic field due to moving charges (Oersted’s discovery).
  2. The right-hand thumb rule states that if you grip a current-carrying wire with your thumb pointing in the current’s direction, your fingers curl in the magnetic field’s direction.
  3. Electric fields arise from charges, while magnetic fields arise from moving charges or magnetic dipoles.
  4. Electromagnetic induction is the production of an EMF in a conductor when exposed to a changing magnetic field.
  5. Self-inductance is the property of a coil to oppose changes in current flowing through itself.
  6. Mutual inductance is the induction of EMF in a coil due to current change in a nearby coil.
  7. A solenoid is a coil of wire that generates a uniform magnetic field when current passes through it.
  8. An electric motor works on the principle that a current-carrying conductor in a magnetic field experiences a force (Lorentz force).
  9. A transformer works on electromagnetic induction, stepping up/down AC voltage by varying the turns ratio.
  10. Eddy currents are loops of induced current in conductive materials exposed to changing magnetic fields.

Advanced Electromagnetism

  1. Maxwell’s equations describe how electric and magnetic fields interact and propagate as electromagnetic waves.
  2. The Lorentz force combines electric and magnetic forces on a charged particle: F = q(E + v × B).
  3. The Poynting vector represents the directional energy flux (power per unit area) of an EM field.
  4. Displacement current (added by Maxwell) accounts for changing electric fields producing magnetic fields.
  5. The skin effect is the tendency of AC current to flow near a conductor’s surface, increasing resistance.
  6. Hysteresis is the lagging of magnetization behind the magnetizing field in ferromagnetic materials.
  7. Permittivity (ε) measures a material’s electric polarizability; permeability (μ) measures magnetic polarizability.
  8. Diamagnetic materials repel magnetic fields; paramagnetic materials weakly attract them.
  9. Ferromagnetic materials (e.g., iron) strongly attract magnetic fields and retain magnetization.
  10. Electromagnetic radiation consists of oscillating electric and magnetic fields (e.g., light, radio waves).

Applications

  1. Speakers convert electrical signals to sound using a coil and magnet that vibrate a diaphragm.
  2. MRI machines use strong electromagnets to align hydrogen nuclei in the body for imaging.
  3. Generators produce electricity by rotating a coil in a magnetic field (Faraday’s law).
  4. Relays use an electromagnet to mechanically switch circuits on/off.
  5. Wireless chargers transfer energy via inductive coupling between coils.
  6. Electromagnets in cranes lift heavy metallic objects by generating strong magnetic fields.
  7. Induction cookers heat pots via eddy currents induced in conductive cookware.
  8. Electromagnetic braking uses induced currents to create opposing magnetic fields, slowing motion.
  9. Antennas transmit signals by converting electrical energy into electromagnetic waves.
  10. Fiber optics use total internal reflection, guided by EM wave principles, to transmit data.

Mathematical Problems

  1. F = k·q₁q₂/r² = (9×10⁹)·(2×3)/1² = 5.4×10¹⁰ N (repulsive if charges are like).
  2. B = μ₀I/(2πr) = (4π×10⁻⁷×5)/(2π×0.1) = 1×10⁻⁵ T.
  3. B = μ₀nI = (4π×10⁻⁷)×(1000/1)×2 ≈ 2.5×10⁻³ T (assuming length = 1m).
  4. V₂/V₁ = N₂/N₁ → V₂ = 220×(50/200) = 55V.
  5. Energy = ½CV² = ½×(10×10⁻⁶)×(100)² = 0.05 J.

Key Takeaways (Expanded)

✔ Maxwell’s equations unify electricity, magnetism, and light.
✔ Faraday’s/Lenz’s laws underpin generators and transformers.
✔ Lorentz force explains motor operation and particle motion in fields.
✔ Eddy currents enable applications like braking and induction cooking.
✔ Permeability/permittivity define material responses to EM fields.
✔ EM waves propagate at light speed (3×10⁸ m/s)

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