test of test of ncert first part.doc

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Sample Paper 2011Class XII

Subject Physics

TEST OF CHAPTERS 1,2,3,4 & 5 OF NCERT ( DO ANY 20 QUESTIONS) M.M- 0

Q:1 A molecule of a substance has a permanent electric dipole moment of magnitude 1029 C m. A mole of this substance ispolarised (at low temperature b! appl!ing a strong electrostatic field of magnitude 10" # m1. $he direction of the field is

suddenl! changed b! an angle of "0%. &stimate the heat released b! the substance in aligning its dipoles along the new

direction of the field. 'or simplicit! assume 100) polarisation of the sample

Q:2 A spherical conducting shell of inner radius r1 and outer radius r2 has a charge Q. (a A charge q is placed at the centre

of the shell. *hat is the surface charge densit! on the inner and outer surfaces of the shell+ (b ,s the electric field inside a

ca-it! (with no charge ero e-en if the shell is not spherical but has an! irregular shape+ &/plain.

Q!3 A c!lindrical capacitor has two coa/ial c!linders of length 1 cm and radii 1. cm and 1. cm. $he outer c!linder is

earthed and the inner c!linder is gi-en a charge of 3.4C. 5etermine the capacitance of the s!stem and the potential of the

inner c!linder. 6eglect end effects (i.e. bending of field lines at the ends.

Q!4$wo charged conducting spheres of radii a and b are connected to each other b! a wire. *hat is the ratio of electric

fields at the surfaces of the two spheres+ 7se the result obtained to e/plain wh! charge densit! on the sharp and pointed

ends of a conductor is higher than on its flatter portions.

Q!5 A small sphere of radius r1 and charge q1 is enclosed b! a spherical shell of radius r2 and charge q2. 8how that if q1 is

positi-e charge will necessaril! flow from the sphere to the shell (when the two are connected b! a wire no matter what thcharge q2 on the shell is.

Q! $he resistance of the platinum wire of a platinum resistance thermometer at the ice point is and at steam point

is.23 . *hen the thermometer is inserted in a hot bath the resistance of the platinum wire is .9 . Calculate the

temperature of the bath.

Q: A resistance ofR draws current from a potentiometer. $he potentiometer has a total resistanceR0 . A -oltage V is

supplied to the potentiometer. 5eri-e an e/pression for the -oltage acrossR when the sliding contact is in the middle of the

potentiometer.

Q:; $wo wires of e 2."3 ? 10; mCu > 1.2

? 10; m @elati-e densit! of Al > 2. of Cu > ;.9.

Q!" shows a potentiometer with a cell of 2.0 # and internal resistance 0.0 maintaining a potential drop across the

resistor wire A. A standard cell which maintains a constant emf of 1.02 # (for -er! moderate currents upto a few mA

gi-es a balance point at ".3 cm length of the wire. $o ensure -er! low currents drawn from the standard cell a -er! high

resistance of "00 Bis put in series with it which is shorted close to the balance point. $he standard cell is then replacedb! a cell of unBnown emf & and the balance point found similarl! turns out to be at ;2.3 cm length of the wire.

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Q:9 A straight wire of mass 200 g and length 1. m carries a current of 2 A. ,t is suspended in midair b! a uniformhoriontal magnetic field #.*hat is the magnitude of the magnetic field+

Q:10 A solenoid of length 0. m has a radius of 1 cm and is made up of 00 turns. ,t carries a current of A. *hat is the

magnitude of the magnetic field inside the solenoid+

Q!11 A 100 turn closel! wound circular coil of radius 10 cm carries a current of 3.2 A. (a *hat is the field at the centre of

the coil+ (b *hat is the magnetic moment of this coil+ the coil is placed in a -ertical plane and is free to rotate about a

horiontal a/is which coincides with its diameter. A uniform magnetic field of 2$ in the horiontal direction e/ists such tha

initiall! the a/is of the coil is in the direction of the field. $he coil rotates through an angle of 90% under the influence of the

magnetic field. (c *hat are the magnitudes of the tor 9.; m s2.

Q!15 $he wires which connect the batter! of an automobile to its starting motor carr! a current of 300 A (for a short time*hat is the force per unit length between the wires if the! are 0 cm long and 1. cm apart+ ,s the force attracti-e or

repulsi-e+

Q!1 A uniform magnetic field of 1. $ e/ists in a c!lindrical region of radius10.0 cm its direction parallel to the a/is

along east to west. A wire carr!ing current of .0 A in the north to south direction passes through this region. *hat is the

magnitude and direction of the force on the wire if (a the wire intersects the a/is (b the wire is turned from 68 to

northeastnorthwest direction (c the wire in the 68 direction is lowered from the a/is b! a distance of ".0 cm+

Q!1$ A solenoid "0 cm long and of radius .0 cm has 3 la!ers of windings of 300 turns each. A 2.0 cm long wire of mass

2. g lies inside the solenoid (near its centre normal to its a/is both the wire and the a/is of the solenoid are in thehoriontal plane. $he wire is connected through two leads parallel to the a/is of the solenoid to an e/ternal batter! which

supplies a current of ".0 A in the wire. *hat -alue of current (with appropriate sense of circulation in the windings of thesolenoid can support the weight of the wire+g > 9.; m s2.

Q!1" A gal-anometer coil has a resistance of 12 and the metre shows full scale deflection for a current of 3 mA. =ow

will !ou con-ert the metre into a -oltmeter of range 0 to 1; #+

Q:19A gal-anometer coil has a resistance of 1 and the metre shows full scale deflection for a current of mA. =ow wi

!ou con-ert the metre into an ammeter of range 0 to " A+

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A short bar magnet placed with its a/is at 30% with an e/ternal field of ;00 D e/periences a tor

test of test of ncert first part.doc

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