Optionals IAS Mains Physics: Questions 274 - 279 of 307

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Question 274

Appeared in Year: 2015

Describe in Detail

Essay▾

Draw the device structure of a junction solar cell and explain how light energy is converted into electrical energy. Draw and explain its charecteristics.

Explanation

The solar cell is a device based on photovoltaic effect. The solar cell generally consist of a junction, where onto its base region, an n-region is diffused as shown in figure (1) . It can be other way also. For crystalline silicon solar cells, the bottom side is totally covered and the front side is partially covered by metal layers. Metal layer…

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Question 275

LR, CR and LCR Circuits-Series and Parallel Resonance

Appeared in Year: 1999

Describe in Detail

Essay▾

An L-C-R circuit has a resistance of , a capacitance of and an inductance of 5H. An ac source is connected in the circuit. Calculate the average power dissipated.

Explanation

Average power

Where is known as the power factor.

Given

Question 276

Euler's Equation of Motion of a Rigid Body
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Appeared in Year: 2015

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Essay▾

Write down Poiseuille՚s formula and mention its limitations in analyzing the flow of liquid through a capillary tube.

Explanation

Rate of liquid-flow through the narrow tube

= coefficient of viscosity of liquid.

r = radius of narrow horizontal tube.

= length

= pressure difference cross the two ends of the tube.

There are two important sources of error in the simple poiseuille՚s experiment:

(1) The liquid flow all along the length of capillary flow tube (T) is not uniform or str…

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Question 277

Appeared in Year: 2003

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Essay▾

Consider an infinite grounded conducting plane. If a point change is held at a distance from the plane, compute by method of images, the electric potential above the plane and induced changes on the conductor. (Marks: 20)

Explanation

We suppose that the conducting plane is specified by and the point charge is located at . If we now imagine a point charge at , it is the required, ‘image charge’ for the problem. This is because when we have a pair of equal and opposite point charges, the surface perpendicular to the line joining them and midway b/w then is a zero potential sur…

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Question 278

Appeared in Year: 2015

Write in Short

Short Answer▾

If and energy levels of platinum are approximately and respectively, below the vacuum level, calculate the wavelengths of and Lines. (Marks: 10)

Question 279

Edit

Appeared in Year: 2003

Describe in Detail

Essay▾

Draw a bcc lattice: Determine its primitive lattice vectors and calculate the packing fraction.

(Marks: 12)

Explanation

The conventional unit cell of bcc structure is non primitive and is drawn in Fig 1. It has cubical shape with atoms located at the corners and the body centre. Thus, the effective number of atoms per unit cell is . The coordination number of each atoms is . The atoms touch one another along the body diagonal. Thus is related to as

The packing fra…

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