Term-1 Physics(Test)

Term-1 Examination – 2021-22

Practice Paper

Subject – Physics

Class - XII

TIME 90 Minutes MAXIMUM MARKS 35

General Instructions:

The Question paper contains three sections.
Section A has 17 questions. Attempt any 15 questions.

(3) Section B has 17 questions. Attempt any 15 questions.

(4) Section C has 6 questions. Attempt any 5 questions.

(5) All questions carry equal marks.

(6)There is no negative marking.

SECTION A

This section consists of 17 multiple choice questions with overall choice to attempt any 15 questions. In case more than desirable number of questions are attempted, only first 15 will be considered for evaluation.

Q1 The SI unit of gyro magnetic ratio is

a) Unit less b) C/kg

c) N/V d) Am²

Q2 The coil of a moving coil galvanometer is wound over a metal frame in order to

a) reduce hysteresis b) increase sensitivity

c) increase moment of inertia d) provide electromagnetic damping

Q3 An electric dipole of dipole moment p is placed parallel to the uniform electric field. The amount of work done in rotating the dipole by 180⁰is

a) 2pE b) pE

c) zero d) pE/2

Q4 The magnetic flux linked with the coil is given by 5t²+6t+10 The induced EMF in the coil at time t=1 will be -

A) -16V b) -43V

c) -108V d) 210V

Q5 Two wires of the same length are shaped into a square of side 'a' and a circle with radius 'r'. If they carry current I and 2I respectively, the ratio of their magnetic moment is

a) 2:π b) π:8

c) π:4 d) 4:π

Q6 The horizontal component of magnetic field of earth at equator is-

a) H=B b) H=V

c) H=0 d) H=√V

Q7 If the number of turns of an inductor are doubled and core length is increased to four times, then it's self inductance will be-

a) Unaffected b) doubled

c) halved d) quadrupled

Q8 Resonance can be achieved in-

a) LR-Circuit b) RC-Circuit

c) LCR-Circuit d) All the above

Q9.By increasing the temperature the specific resistance of a semiconductor-

a) increases b) no effect

c) decreases d) first increases then becomes constant.

Q10 What is the angle between the electric dipole moment and the electric field strength due to it on the equatorial line

a) zero b) 90⁰

c) 180⁰ d) None of the above

For question numbers 11, 12, 13,14 and 15 two statements are given-one labeled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below:

(a) Both A and R are true and R is the correct explanation of A.

(b) Both A and R are true but R is not the correct explanation of A.

(d) A is false and R is also false.

11. Assertion (A): The charge on any body can be increased or decreased in terms of 'e'.

Reason (R): Quantisation of charge means that the charge on a body is the integral multiple of 'e'.

12. Assertion (A):The electric field inside a cavity is always zero.

Reason (R) : Charge reside only on the outer surface of a conductor with cavity.

13. Assertion (A) : To increase the range of an ammeter, we must connect a suitable low resistance in parallel to it.

Reason (R) : The ammeter with increased range should have high resistance.

14. Assertion (A) : On increasing the current sensitivity of a galvanometer by increasing the number of turns ,may not necessarily increase its voltage sensitivity .

Reason (R): The resistance of the coil of the galvanometer increases on increasing the number of turns.

15. Assertion (A) : A magnetic needle free to rotate in a vertical plane,orients itself vertical at the poles of the earth.

Reason (R): At the poles of the earth the vertical component of earth's magnetic field will be zero.

16.The transmission ratio for step -up transformer is-

a) k=1 b) k>1

c) k<1 d) none of the above

17)A coil and a bulb are connected in series with a DC source ,a soft iron core is inserted in the coil,then the intensity of the bulb-

a) is same b) increases

c) decreases d) zero

SECTION-B

This section consists of 17 multiple choice questions with overall choice to attempt any 15 questions.In case more than desirable number of questions are attempted, only first 15 will be considered for evaluation

18) A conducting rod of length l is falling with a constant velocity v perpendicular to uniform horizontal magnetic field B. The force acting on the rod is-

a) F=0 b) F=mg

c) F=qvB d) F=B²l²v²/R

19) The physical quantity that has same dimension as that of √LC is-

a) length b) mass

c) resistance d) time period

20) Bandwidth of the resonant LCR circuit is-

a) R/L b) R/2L

c) 2R/L d) 4R/L

21) Which quantities do not change during transformer operation-

a) power b) frequency

c) voltage d) both a and b

22)A transformer has 150 turns in its primary and 1000 in secondary.If the primary is connected to 440V dc supply, what will be the induced voltage in the secondary ?

a) 10V b) 3V

c) 5V d) zero

23) The potential of a large liquid drop when eight liquid drops are combined is 20V,then the potential of each single drop was-

a) 10V b) 7.5V

c) 5V d) 2.5V

24) The potential of an electric dipole varies with distance r as-

a) 1/r² b) 1/r

c) 1/r³ d) r

25)The electrostatic potential energy between proton and electron separated by a distance of 1A⁰ is-

a) 13.6ev b) 27.2eV

c) -14.4eV d) 1.4ev

26)A pair of adjacent coils has a mutual inductance of 1.5H.If the current in one changes from 0 to 20A in 0.5s,what is the change of flux with the other coil ?

a) zero b) 10wb

c) 20wb d) 30wb

27)A metallic rod of 1m is rotated with frequency of 50rev/s,with one end hinged at the centre and the other at the circumference of a circular metallic ring of radius 1m,about an axis passing through the centre and perpendicular to the plane of the ring.A constant and uniform magnetic field of 1T parallel to the ring axis is present everywhere.What is the emf between the centre and metallic ring?

a) zero b) 100V

c) 157V d) 325V

28)A galvanometer coil has a resistance of 15ohm and the metre shows full scale deflection for a current of 4mA.It can be converted into ammeter of range 0 to 6A by connecting a shunt of-

a) 10ohm b) 10m ohm

c) 1000ohm d) 100m ohm

29)A power transmission line feeds input power at 2200V to a step down transformer with its primary windings having 3000 turns.The number of turns in the secondary in order to get output power at 220V are-

a) 4 b) 30

c) 300 d) 3000

30)The principle of working of transformer is-

a) self induction b) induction

c) mutual induction d) All the above

31) Power factor in LCR circuit is given by-

a) zero b) unity

c) R/Z d) Z/R

32)The best instrument for accurate measurement of EMF of a cell is-

a) metre bridge b) Voltmeter

c) ammeter d) potentiometer

33)A galvanometer coil has a resistance of 12ohm and the metre shows full scale deflection for a current of 3mA.It can be converted into a voltmeter of range 0 to 18V by connecting a high resistance of

a) 6000ohm b) 5988ohm

c) 1000ohm d) 5000ohm

34) A parallel plate capacitor with air between the plates has a capacitance of 8pF.What will be the capacitance if the distance between the plates is reduced by half, and the space between them is filled with a substance of dielectric constant 6?

a) 230pF b) 105pF

c) 96pF d) 8pF

SECTION-C

This section contains of 6 multiple choice questions with an overall choice to attempt any 5.In case more than desirable number of questions are attempted,only first 5 will be considered for evaluation.

ELECTROSTATIC SHIELDING:

The phenomenon of making a region free from any electric field is called electrostatic shielding or electrostatic screening.It is base on the fact that electric field becomes zero inside the cavity of hollow conductor.In a hollow conductor charges are distributed on the surface of conductor.Such a field free region is also called a Faraday Cage.Such a cage can block the effects of external field on its internal contents,or the effects of an internal field on the outside environment.Inside the Faraday cage ,electric field is always zero.Even if the conductor is charged or charges are induced on a neutral conductor by an external field ,all charges reside only o the outer surface of the conductor.Hence , any cavity of any shape and size is always shielded from outer electric region.

35) In a region of constant potential

(a) the electric field is uniform (b) the electric field is zero

36) If a conductor has non-zero potential and there are no charges anywhere else outside,then

(a) there must be charges on the surface or inside itself.

(b) there cannot be any charge in the body of the conductor.

(d) both (a) and (b).

37) The work done in carrying a charge Q once round a circle of radius r with charge q at the centre of the circle is

(a) kQ/r (b) kQq/r

38) At a point A, there is a electric field of 500V/m and potential difference of 3000V.The distance between the point charge and A is

(a) 6m (b) 36m

39) The electric field intensity on the surface of a uniformly charged conductor is-

a) zero b) qF