Electromagnetic Theory And Electronics

i. Paramagnetic Substances

Step 1: Paramagnetic materials have unpaired electrons in their atomic structure, which cause weak attraction to external magnetic fields.

Step 2: They have a small and positive magnetic susceptibility and align weakly with the applied magnetic field. Examples: Aluminum, Platinum, Oxygen.

ii. Diamagnetic Substances

Step 1: Diamagnetic materials have all paired electrons, causing them to create an induced magnetic field in the opposite direction to the applied field.

Step 2: They have a small and negative magnetic susceptibility and are weakly repelled by the applied magnetic field.

Examples: Copper, Gold, Bismuth.

iii. Ferromagnetic Substances

Step 1: Ferromagnetic materials have domains of atoms that align strongly with an external magnetic field, creating a strong attraction.

Step 2: They have high positive susceptibility and retain magnetization even after removing the external field.

Examples: Iron, Nickel, Cobalt.

Step 1: Magnetic flux ( ) linked with a coil depends on: where:
- = Magnetic field strength
- = Area of the coil
- = Angle between the field and the normal to the coil

(i) Cause
Solution: The changing magnetic field causes an induced electromotive force (EMF).

Step 1: According to Faraday's law, EMF is induced when the magnetic flux through a coil changes with time.

(ii) Magnitude
Solution: The magnitude of induced EMF is proportional to the rate of change of flux.

Step 1: Using Faraday's law, the magnitude of the induced EMF is:

Step 2: Faster changes in flux result in higher EMF.

(iii) Direction
Solution: The direction of induced EMF is given by Lenz's Law.

Step 1: According to Lenz's Law, the induced EMF opposes the change in magnetic flux.

Step 2: The negative sign in Faraday's law signifies this opposition.

A transformer works on the principle of electromagnetic induction.

Step 1: An alternating current in the primary coil creates a changing magnetic field.

Step 2: This varying magnetic flux induces an EMF in the secondary coil according to Faraday's law.

(i) Leakage of magnetic flux
Solution: There should be no flux leakage; all flux should link both coils.

Step 1: Ideally, all magnetic flux produced by the primary coil should pass through the secondary coil.

(ii) Resistance of primary coilSolution: The primary coil should have zero resistance.

Step 1: An ideal transformer assumes no resistive losses in the primary coil to prevent energy dissipation.

(iii) Resistance of secondary coil
Solution: The secondary coil should also have zero resistance.

Step 1: In an ideal transformer, the secondary coil is assumed to be perfect, with no resistance.

(iv) Dissipation of power

Solution:
There should be no power loss in an ideal transformer.
Step 1: In an ideal transformer, the entire power input is transferred to the output. Step 2: Efficiency is 100%, meaning no loss due to resistance, flux leakage, or core losses.