CBSE - XII Physics 2005 Question Paper

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CBSE Examination 2009

CBSE - XII Physics 2005 Question Paper

Author: deepa mittal

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Physics (Theory)

Time allowed : 3 hours

Maximum Marks : 70

General Instructions :

All questions are compulsory.
There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and one question of five marks. You have to attempt only one of the choices in such questions
Question numbers 1 to 5 are very short answer type questions, carrying one mark each
Question numbers 6 to 12 are short answer type questions, carrying two marks each.
Question numbers 13 to 24 are also short answer type questions, carrying three marks each.
Question numbers 13 to 24 are also short answer type questions, carrying three marks each.
Use of calculators is not permitted. However, you may use log tables, if necessary.
You may use the following values of physical constants wherever necessary :
$c=3 * 10^8 ms^{-1}$
$h=6.6*10^{-34}Js$
$e=1.6*10^{-19}C$
$m_e=9.1*10^{-31} Kg$
$\mu _0 = 4 \pi *10^{-7}T mA^{-1}$
$\frac {1}{4 \pi \epsilon _0}=$
Mass of neutron $m_n \cong 1.6 *27^{-27} kg$
Boltzmann's constant $K=1.38*10^{23} JK^{-1}$
Avogadro's number $N_A=6.023*10^{23} / mole$

PART A

An electric dipole of dipole moment $20*10^{-6}$ is enclosed by a closed surface. What is the net flux coming out of the surface ?
An electron beam projected along + X-axis, experiences a force due to a magnetic field along the + Y-axis. What is the direction of the magnetic field ?
The power factor of an a.c. circuit is 0.5. What will be the phase difference between voltage and current in this circuit ?
Electrons are emitted from a photosensitive surface when it is illuminated by green light but electron emission does not take place by yellow light. Will the electrons be emitted when the surface is illuminated by (i) red light, and (ii) blue light ?
What should be the length of the dipole antenna for a carrier wave of frequency
Define 'electric line of force' and give its two important properties.
(a) Why does the electric field inside a dielectric decrease when it is placed in an external electric field ?

A parallel plate capacitor with air between the plates has a capacitance of 8 pF. What will be the capacitance if the distance between the plates be reduced by half and the space between them is filled with a substance of dielectric constant K = 6 ?

OR

Three point charges of $+ 2 \mu C, - 3 \mu C$ and $-3 \mu C$ are kept at the vertices, A, B and C respectively of an equilateral triangle of side 20 cm as shown in the figure. What should be the sign and magnitude of the charge to be placed at the mid-point (M) of side BC so that the charge at A remains in equilibrium ?
Draw V-I graph for ohmic and non-ohmic materials. Give one example for each.
Define the terms 'Magnetic Dip' and 'Magnetic Declination' with the help of relevant diagrams.

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