# Electricity and Magnetism [Optionals IAS Mains Physics]: Questions 1 - 6 of 20

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## Question 1

Electricity and Magnetism
Self and Mutual Inductances
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Appeared in Year: 2012 (IFS)

### Describe in Detail

Essay▾

Explain the term ‘mutual inductance’ between two coils carrying current. Describe a method of determining mutual inductance between two coils of wire with relevant theory. (Paper-1) (Section-B)

### Explanation

• By changing magnetic field around turns of an inductor, an emf induced in it and this emf is also induced in the same circuit by changing in current, this effect is called Self-induction (L) .
• When a coil in which emf induced situated in the region of the same magnetic field, the induced emf is called Mutual induction. If two or more coils are magne…

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## Question 2

Electricity and Magnetism
Laplace and Poisson Equations

Appeared in Year: 2002

### Describe in Detail

Essay▾

Calculate the electric field for a point on the axis of a charged ring having charge ‘q’ and Radius a show that the maximum value occur at . (20 Marks)

### Explanation

Consider a circular loop of wire of negligible thickness, radius a and centre O held perpendicular to the plane of the paper. Let the loop carry a total charge + q distributed uniformly over its circumference. We have to determine electric field intensity at on axis of the loop, where .

Consider a small element AB of the loop. Let length of element…

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## Question 3

Electricity and Magnetism
Energy of a System of Charges

Appeared in Year: 2002

### Describe in Detail

Essay▾

Show that the potential energy of a charge Q uniformly distributed throughout the sphere of radius R is given by (20 marks)

### Explanation

• Let as assume that the sphere has Radius R and ultimately will contain a total charge Q uniformly distributed throughout its volume. The electrostatic potential energy U is equal to the work done in assembling the total charge Q within the volume i.e. the work done in bringing Q from infinity to the sphere. We can do this by bringing a series of ve…

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## Question 4

Electricity and Magnetism
LR, CR and LCR Circuits-Series and Parallel Resonance

Appeared in Year: 2010

### Describe in Detail

Essay▾

A series circuit has an inductance of micro henries, a capacitance of microfarad and a resistance of ohms. Fine the resonant frequency and quality factor of the circuit. (20 Marks)

### Explanation

The resonant frequency of series LCR circuit is given by

Quality factor

## Question 5

Electricity and Magnetism
Ferromagnetic Materials
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Appeared in Year: 2000

### Describe in Detail

Essay▾

What are the salient features of ferromagnetic? Explain how the curie law of paramagnetism is modified to Curie-Weiss law? (20 Marks)

### Explanation

• Like paramagnetism, ferromagnetism is also associated with the presence of permanent magnetic dipoles, but unlike paramagnetism, the magnetic moments of adjacent atoms in this case are aligned in a particular direction even in the absence of the applied magnetic field. Thus a ferromagnetic material exhibits a magnetic moment in the absence of a mag…

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## Question 6

Electricity and Magnetism
LR, CR and LCR Circuits-Series and Parallel Resonance

Appeared in Year: 2002

### Describe in Detail

Essay▾

A series LCR circuit with is powered by a source of volts and variable frequency. Find (a) resonant frequency (20 marks)

### Explanation

The resonance frequency is given by

(b) The Quality factor of the circuit ⇾

The Q is given by

(c) The width of resonance is ⇾

(d) The maximum content at resonance.

At resonance Impedance in the circuit = resistance R

Amplitude or peek value of the curents =

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