Subject

Physics

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

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11.

A parallel plate capacitor is being charged by a time varying current. Explain briefly how Ampere’s circuital law is generalized to incorporate the effect due to the displacement current. 


When AC current is passed through capacitor, current moves from one plate to another. According to Ampere’s circuital law, a magnetic field has to exist between the plates of the capacitor for the current transfer to happen. So, Maxwell modified Ampere’s circuital law with the help of continuity equation.

The modified Ampere’s law by Maxwell is given by,

contour integral straight B with rightwards harpoon with barb upwards on top. straight space dl with rightwards harpoon with barb upwards on top straight space equals straight space straight mu subscript straight o straight i straight space plus    straight mu subscript straight o straight epsilon subscript straight o dϕ subscript straight E over dt
space space space space space space space space space space space
space space space space space space space space space space space space equals straight space straight mu subscript straight o straight space left parenthesis thin space straight i straight space plus straight space straight i subscript straight D right parenthesis  


where, iDstraight epsilon subscript straight o dϕ subscript straight E over dtstraight epsilon subscript straight o dϕ subscript straight E over dt, is called the Displacement current.

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12.

Net capacitance of three identical capacitors in series is 1 F. What will be their net capacitance if connected in parallel?

Find the ratio of energy stored in the two configurations if they are both connected to the same source. 
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13.

In the meter bridge experiment, balance point was observed at J with AJ = l.

(i) The values of R and X were doubled and then interchanged. What would be the new position of balance point?

(ii) If the galvanometer and battery are interchanged at the balance position, how will the balance point get affected? 


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14.

Draw a labelled diagram of a full wave rectifier circuit. State its working principle. Show the input-output waveforms. 

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15.

Two heating elements of resistance R1 and R2 when operated at a constant supply of voltage, V, consume powers P1 and P2 respectively. Deduce the expressions for the power of their combination when they are, in turn, connected in (i) series and (ii) parallel across the same voltage supply.

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16.

Write any two characteristic properties of nuclear force.      

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17.

What happens to the width of depletion layer of a p-n junction when it is (i) forward biased, (ii) reverse biased? 

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18.

Define the term ‘stopping potential’ in relation to photoelectric effect. 

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19.

What is sky wave communication? Why is this mode of propagation restricted to the frequencies only up to few MHz?

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20.

Using the curve for the binding energy per nucleon as a function of mass number A, state clearly how the release in energy in the processes of nuclear fission and nuclear fusion can be explained.              

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