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.
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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.


The root mean square (rms) value of a.c. is defined as that value of steady current, which would generate the same amount of heat in a given resistance in a given time, as is done by the a.c. when passed through the same resistance for the same time.

As    I = I0 sin ωt

Here, 

straight H space equals space integral subscript 0 superscript straight T space straight I squared space straight R space dt

straight H space equals space integral subscript 0 superscript straight T space straight I subscript straight o squared space sin space squared space straight omega space straight t space straight R space dt

space space space equals space straight I subscript straight o squared space straight R space integral subscript 0 superscript straight T space open parentheses fraction numerator 1 space minus space cos space 2 ωt over denominator 2 end fraction close parentheses space dt space

space space space equals space fraction numerator straight I subscript straight o squared space straight R space over denominator 2 end fraction space open square brackets integral subscript 0 superscript straight T space dt space minus space integral subscript 0 superscript straight T space cos space 2 ωt space. dt close square brackets

Solving comma space we space get

space straight H equals space fraction numerator straight I subscript straight o squared space RT over denominator 2 end fraction space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space... space left parenthesis straight i right parenthesis space

If space straight I subscript rms space be space the space rms space of space ac comma space then

straight H space equals space straight I squared subscript rms space RT space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space... space left parenthesis ii right parenthesis thin space

From space left parenthesis straight i right parenthesis space and space left parenthesis ii right parenthesis comma

straight I squared subscript rms space RT space equals space fraction numerator straight I subscript straight o squared RT over denominator 2 end fraction space

straight I subscript rms space equals space fraction numerator straight I subscript straight o over denominator square root of 2 end fraction space 

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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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