Electromagnetism

Step 1: Isothermal Expansion.
For isothermal expansion, the pressure and volume follow Boyle's Law, where . So after the isothermal expansion, the pressure is reduced to .
Step 2: Adiabatic Expansion.
For adiabatic expansion, the pressure and volume follow the equation , where . Using this relation, we can find the final pressure: Substituting the values and solving gives:
Step 3: Conclusion.
Thus, the correct answer is (D) .

Step 1: Formula for magnetic field due to revolving electron.
The magnetic field produced at the centre of a circular orbit by a moving electron is given by the formula: where is the permeability of free space, is the charge of the electron, is the angular momentum, is the mass of the electron, and is the radius of the orbit.
Step 2: Conclusion.
Thus, the correct answer is (B) .

Concept:
In a p-n junction, depletion region contains immobile ions creating strong electric field. Step 1: Effect of reverse bias. Reverse bias increases width of depletion region and strengthens electric field.
Step 2: Field distribution. Maximum electric field exists inside depletion layer, especially near junction.
Step 3: Potential variation. Potential increases across depletion region, not zero.
Step 4: Conclusion. Electric field is maximum in depletion layer.

Step 1: Surface Area Change
Initial Area .
Final Area .
From volume conservation: .
Step 2: Substitute n
.
Step 3: Work Done
.
.
Final Answer: (B)