CBSE [All India]-Set-3-2012
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Q1
Two wires of equal length, one of copper and the other of manganin have the same resistance. Which wire is thicker?
Marks:1View AnswerAnswer:
We know that,
Thus, manganin is thicker. -
Q2
A bar magnet is moved in the direction indicated by the arrow between two coils PQ and CD. Predict the directions of induced current in each coil.
Marks:1View AnswerAnswer:
The direction of induced current will be clockwise in both the coils. In first coil, the direction of induced current is from P to Q and in the second coil the direction is from C to D.
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Q3
For the same value of angle of incidence, the angles of refraction in three media A, B and C are 15°, 25° and 35° respectively. In which medium would the velocity of light be minimum?
Marks:1View AnswerAnswer:
Therefore, velocity of light is minimum in medium ‘A’. -
Q4
A proton and an electron have same kinetic energy. Which one has a greater de-Broglie wavelength and why?
Marks:1View AnswerAnswer:
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Q5
Mention the two characteristic properties of the material suitable for making core of transformer?
Marks:1View AnswerAnswer:
Two characteristic properties of the material suitable for making core of transformer are:
(i) It should have low coercivity and low retentivity.
(ii) It should have a smaller hysteresis loop. -
Q6
A charge ‘q’ is placed at the centre of a cube of side l. What is the electric flux passing through each face of the cube?
Marks:1View AnswerAnswer:
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Q7
How does the fringe width, in Young’s double-slit experiment, change when the distance of separation between the slits and screen is doubled?
Marks:1View AnswerAnswer:
On doubling the distance of separation between the slits and screen, the fringe width becomes twice.
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Q8
The speed of an electromagnetic wave in a material medium is given by
being the permeability of the medium and 
its permittivity. How does its frequency change?Marks:1View AnswerAnswer:
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Q9
An electric dipole is held in a uniform electric field.
(i) Show that the net force acting on it is zero.
(ii) The dipole is aligned parallel to the field. Find the work done in rotating it through an angle of 180°.Marks:2View AnswerAnswer:
(i)
(ii) W = change in potential energy
= Ufinal – Uinitial
= (–pE cos180°) – (–pE cos0°)
= 2pE -
Q10
State the underlying principle of a transformer. How is the large scale transmission of electric energy over long distances done with the use of transformers?
Marks:2View AnswerAnswer:
A transformer is based on principle of mutual induction which states that due to continuous change in the current in the primary coil, an emf gets induced across the secondary coil.
Electric power generated at the power station, is stepped up to a very high voltage by means of a step-up transformer and transmitted to a distant place. At receiving end, it is stepped down by a step down transformer.
