Subject

Physics

Class

ICSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

Download the PDF Sample Papers Free for off line practice and view the Solutions online.
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 Multiple Choice QuestionsShort Answer Type

41. The following equation represents a fusion reaction :

straight H presubscript 1 presuperscript 2 space plus space straight H presubscript 1 presuperscript 3 space rightwards arrow space He presubscript 2 presuperscript 4 space plus space straight n presubscript 0 presuperscript 1 space plus space straight Q space semicolon

space where space straight Q space is space the space enrgy space released

Mass space of space straight H presubscript 1 presuperscript 2 space space atom space equals space 2.014102 space straight u

Mass space of space straight H presubscript 1 presuperscript 3 space atom space equals space 3.016050 space straight u

Mass space of space He presubscript 2 presuperscript 4 space atom space equals space 4.002603 space straight u

Mass space of space space neutron space space straight n presubscript 0 presuperscript 1 space equals space 1.008665 space straight u

Calculate the value of Q.

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42. What is a Zener diode? Explain how it can be used to stabilise the voltage in a circuit.


Zener diode : A zener diode is a specially designed junction diode which can operate continuously, without being damaged in the region of reverse breakdown voltage. Symbolically, it is represented as follows.



One of the most important application of Zener diode is the design of constant voltage power supply.

The Zener diode is joined in reverse bias to the d.c. but through a resistance R of suitable value.

Output is taken across a load resistance R
L in parallel with the diode.

When the fluctuating d.c. increases beyond a certain limit, the current through the zener diode circuit rises sharply.

Therefore, there is an increase in voltage drop across R.

Hence the voltage drop across the Zener diode and across the load resistance R
L falls is normal value.
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43. The output of an OR gate is connected to the input of a NOT gate. Draw the logic circuit of this combination and write its truth table.  
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 Multiple Choice QuestionsLong Answer Type

44.

The current flowing through a conductor is given by I = neAvd

(i) Identify each term in the equation.

(ii) Obtain an expression for vd, if the current flowing through the conductor of length I has its ends maintained at a potential difference of V volts.

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45.

(i) Write an expression for Biot-Savart’s law in the vector form. Write an expression for the magnetic field at the centre of a circular coil of radius R, with N turns and carrying a current I. 

(ii) A helium nucleus completes one round of a circle of radius 0.8 m in 2 seconds. Find the magnetic field at the centre of the circle.

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46. Show that straight I subscript rms space equals space fraction numerator straight I subscript straight o over denominator square root of 2 end fraction where Irms is the root mean square value of alternating current and I0 is its peak value.
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47.

(i) Derive an expression for the fringe width ‘y’ in Young’s double slit experiment. Use X as the wavelength of the monochromatic source, D as the distance of the screen from the slits and d as the distance of separation between the slits.

(ii) How does the fringe pattern change if the monochromatic source of light in the above experiment is replaced by a white source of light ?

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