# CBSE [All India]-Set-1-2013

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• Q1

Write the expression for the de Broglie wavelength associated with a charged particle having charge ‘q’ and mass ‘m’ when it is accelerated by a potential V.

Marks:1

• Q2

The graph shown in the figure represents a plot of current versus voltage for a given semiconductor. Identify the region, if any, over which the semiconductor has a negative resistance.

Marks:1

Resistance of a material can be determined by the slope of the curve formed between voltage V and current I. Here, portion BC indicates the negative resistance.

• Q3

Two charges of magnitudes +4Q and –Q are located at points (a,0) and (-3a,0) respectively. What is the electric flux due to these charges through a sphere of radius ‘2a’ with its centre at the origin?

Marks:1

• Q4

The motion of copper plates is damped when it is allowed to oscillate between the two poles of a magnet. If slots are cut in the plate, how will the damping be affected?

Marks:1

The motion of copper plate is damped due to eddy currents which are generated inside the plate. If slots are cut in the plate then the damping will reduce which means eddy currents are reduced.

• Q5

Two identical cells, each of e.m.f. E, having negligible internal resistance, are connected in parallel with each other across an external resistance R. What is the current through this resistance?

Marks:1

The given identical cells are arranged as shown in the circuit diagram:

• Q6

How does the mutual inductance of a pair of coils change when
(i) Distance between the coils is decreased and
(ii) Number of turns in the coils is decreased?

Marks:1

(i) On decreasing the distance between the coils, magnetic flux linked with secondary coil due to current flowing through the primary coil will increase. Hence mutual inductance of the coil will also increase.

(ii)

• Q7

Define the activity of a given radioactive substance. Write its S.I. unit.

Marks:1

The total decay rate of radioactive sample is known as the activity of the sample substance. The S.I. unit of radioactivity is Becquerel (Bq).

• Q8

Welders wear special goggles or face masks with glass windows to protect their eyes from electromagnetic radiations. Name the radiations and write the range of their frequency.

Marks:1

Welder uses some unique goggles with glass windows to shield the eyes from harmful ultra violet radiations (UV rays). The range of UV rays is 4×10-7 m (400nm) to 6×10-10 m (0.6nm).

• Q9

In the circuit shown in the figure, identify the equivalent gate of the circuit and make its truth table.

Marks:2

Truth Table:

 A B A’ B’ Y’ Y 1 1 0 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 0 0 1 1 1 0

• Q10

Explain the term ‘drift velocity’ of electrons in a conductor. Hence obtain the expression for the current through a conductor in terms of ‘drift velocity’.

Marks:2