Arun had repaint his car when he was remined by the car company for his regular car service. He told them to do spray painting of mountain dew colour. The company also replied that they usually perform spray painting only as wastage is minimised and painting achieved. |
(i) What values do the car company have? |
(ii) If spray painting is done by electrostatic induction, how is even painting achieved? |
Saurabh and his family went for an outing. On the way Saurabh's grandfather lost his spectacles. He was facing difficulty in reading book. Saurabh was carrying a magnifying lens carry out a Biology project. He gave it to his grandfather and solved his difficulty. |
(i) What qualities are exhibited by Saurabh? |
(ii) Previously his grandfather was using spectacles of power \[=-1D\] for distant vision. Now, he also needs to use reading glass of \[+\,0.2.\] Explain it. |
Two kids were discussing blowing soap bubbles with spectacular colouring. Ravi, an M.Sc. (Physics) student was watching them. He explained the phenomenon to the kids. |
(i) What kind of person is Ravi? |
(ii) Why are colours formed on bubbles? Name the phenomenon. |
If a point charge \[+\,q\] is taken first from A to C and then from C to B of a circle drawn with another point charge \[+\,q\] at the centre, in below figure, then along which path, more work will be done? |
Or |
A point charge causes an electric flux of \[-1\times {{10}^{3}}N{{m}^{2}}{{C}^{-1}}\] to pass through a spherical Gaussian surface of 10 cm radius centered on the charge. |
(i) How much flux will pass through the surface, if the radius of the Gaussian surface is doubled? |
(ii) Find the value of the point charge. |
Can a straight wire act as an inductor? Two identical loops, one of copper and other of aluminium are rotated with the same speed, in a uniform magnetic field acting normal to the plane of the loops. State with reasons, for which of the coils |
(i) induced emf, will be more. |
(ii) induced current, will be more. |
(i) Why does the sky appear blue? |
(ii) Explain by giving reason, why the sun looks reddish at sunrise and sunset. |
A series L-C-R circuit is connected to a 220V variable frequency AC supply. If L = 20 mH, |
\[C=\left( \frac{800}{{{\pi }^{2}}} \right)\mu F\] and \[R=110\,\Omega .\] |
(i) Find the frequency of the source for which average power absorbed by the circuit is maximum. |
(ii) Calculate the value of maximum current amplitude. |
Draw a graph showing the variation of stopping potential with the frequency of incident radiation in regarting to photoelectric effect. |
(i) What does the slope of this graph represent? |
(ii) How can the value of work function of the material be determined from this graph? |
Or |
The work function for the following metals is given, Na: 2.75 eV; K : 2.30 eV; Mo : 4.17 eV Ni : 5.15 eV Which of these metals will not give photoelectric emission for a radiation of wavelength \[3300\text{ }\overset{{}^\circ }{\mathop{A}}\,\] from a He-Cd laser placed 1m away from the photocell? What happens, if the laser is brought nearer and placed 50 cm away? |
Physics teacher Mr. Hassan has given three lenses of power 2D, 4D and 10D to a student Ramesh. Ramesh was not sure as to which lenses would he use for constructing a good astronomical telescope. So, he consults his seniors and the teacher and then constructs a telescope. Later, he shows this telescope to the junior classes and explain about the choice of lenses. |
Read the above passage and give the answer of the following questions. |
(i) What values has Ramesh shown by doing these? |
(ii) Which lenses are used as objective and which one as eyepiece? |
(iii) Write two applications of astronomical telescope. |
Shankar complained of a severe stomach pain and started crying. His elder brother brought him to a gastroenterologist. The doctor advised for an endoscopy and asked him to come the next day on an empty stomach. The test was done and Shankar felt okay after taking medicine. |
(i) What values of Shankar's elder brother impress you? |
(ii) What is the working principle of the glass fibre in the endoscope? |
(iii) Write down conditions for total internal reflection. |
(i) Some scientist have predicted that a global nuclear war on the earth would be followed by nuclear winter. What would cause nuclear winter? |
(ii) Calculate the activity of 1 mg sample of \[{}_{37}Sr{}^{90},\] whose half-life period is 28 yr, |
(iii) Define decay constant. |
Or |
Suppose India has a target of producing by 2020 AD 200,000 MW of electric power, 10 per cent of which is to be obtained from nuclear power plants. Suppose we are given that, on average the efficiency of utilisation (i.e., conversion to electric energy) of thermal energy produced in a reactor is 25%. How much amount of fissionable uranium would our country need per year at the turn of this century? |
Take the heat energy per fission of \[{{U}^{235}}\] to be about 200 MeV Avogadro's number \[{{N}_{A}}=6.023\times {{10}^{23}}mo{{l}^{-1}}.\] |
(i) Use Biot-Savart law to obtain a formula for magnetic field at the centre of a circular loop of radius R carrying a steady current I. Indicate the direction of the magnetic field. |
(ii) A solenoid of length 5m has a radius of 1 cm and is made of 500 turns it carries a current of 5 A. |
What is the magnitude of the magnetic field inside the solenoid. |
Or |
(i) A short bar magnet of magnetic moment \[=\text{ }32\text{ }A{{m}^{2}}\] is placed in a uniform magnetic field of 15 T. If the bar is free to rotate in the plane of field, which orientations would correspond to its |
(a) stable and |
(b) unstable equilibrium? What is the potential energy of the magnet in each case? |
(ii) State Gauss' law in magnetism. |
(iii) Define magnetic susceptibility of a material. Name two elements, one having positive susceptibility and other having negative susceptibility. |
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