# Physics Paper IV Electromagnetism Previous Year Question Paper Year 2005 : IInd Year

**Q. 1. (a)** Define a line integral and a surface integral Obtain an expression for curl of a vector.

**(b) **State and prove Stokes1 theorem.

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**Q. 2.** Stat Coulomb’s law of electrostatics. Hence define unit charge. Obtain an expression for energy of a system of charges and a relation between electromagnetic and gravitational force between electron and proton of a H-atom. What is the S.I. system of units and why is it widely used ?

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**Q. 3. (a)** Discuss transient behaviour of a C-R circuit in detail.

**(b)** Describe a method for finding high resistance by leakage. Why can’t we measure low resistance by this method ?

**(c ) **A condenser of capacity 0.5 p.F is discharged through a resistance of 10 Mil. Find the time taken for half the charge on the condenser to escape (ioge 2 = 0.6931).

**Answer : **

**Q. 4. (a)** State and prove Gauss’s law of electrostatics. Derive its differential form,

**(b) **Derive an expression for the electric field at a point inside a uniformly charged solid sphere.

**Answer : **

**Q. 5. (a) **Define the coefficient of mutual inductance and coefficient of coupling.

**(b) **Give a method for finding coefficient of mutual inductance of two coils. What is the role of the core between two coils?

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**Q. 6. (a) **State Biot-Savart law and hence obtain an expression for the field due to an infinitely long conductor.

**(b) **Write Maxwell’s equations for electromagnetic field.

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**Q. 7. **Define capacity of a conductor. Derive an expression for capacity of a spherical condenser

**(a)** with outer surface earthed,

**(b) **with inner surface earthed.

**Answer : **

**Q. 8.** Write short notes on any two of the following :

(i) em wave equation

(ii) Choke coil

(iii) Dia-, para- and ferro-magnetk substances

(iv) Sensitivity of Wheatstone bridge.

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