Physics practice paper class 12th

 

Practice Paper-1

Class-XII

Physics 

M.M.:70

[Section - A]

1. The charge on an electron is

a) °C

b) 1C

c) 2.6 * 10 ^ - 19 * C

d) - 1.6 * 10 ^ - 19 * C

2. "Ohm-metre" is unit of

a) Resistance

b) Resistivity

c) Current density

d) Conductivity

3.

is a symbol of

a) diode

b) n-type

c) P type

d) Transistor

4. With the increase of temperature, The resistivity of a metal

a) increases

c) may increase or decreases eases

b) decreases

d) does not change

5. Phase difference between voltage and current when an AC source is connected to an inductor

a) O deg

b) 45 deg

c) 90 deg

d) 180 deg

6. The working of a totally reflecting prism is based upon

a) total internal reflection

b) reflection

c) refraction

d) none of these

7. What is a relation between free electrons(ne) holes (nh) in intrinsic semiconductor

a) n_{e} > n_{n}

b) n_{n} > n_{e}

c) n_{e} = n_{n}

d) None

8. Dimensions of capacitance is

a) M ^ - 2 * L ^ - 2 * T ^ - 4 * A ^ 2

b) I * M ^ - 1 * L ^ - 2 * T ^ 4 * A ^ 2

c) M ^ - 1 * L ^ - 2 * T ^ - 2 * A ^ 2

d) M ^ - 1 * L ^ - 2 * T ^ - 4 * A ^ - 2

9. The relation between current density (j) and electric current(I) is

a) j = V_{d}*IA

b) j = A/I

c) j = A/T

d) j = IA

10. Two atoms have same atomic number but different atomic mass. They will be

a) isotopes

b) isotones

c) isobaric.

d) none of these

11. Energy band of substance shown in the figure. Where V is valence band and Cis conduction Band

Substance is

a) metal

b) insulator

c) semiconductor

d) None of these

12. When reversed biased is applied to a PN junction. It

a) raises the potential barrier

b) Increase the majority carrier current

c) lower the potential barrier

d) None of the above

13: When the distance between two magnetic poles is reduced to half the force between them increases by___times.

14. Snell experimentally obtained the laws of___of light.

15. The unit of resistance is___.

Assertion Reason based questions:

Choose the correct option for following assertion reason statements:

(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.

(c) A is true but R is false.

(d) A is false but R is true.

16. Assertion: In gravity within a conductor, the electric field is zero

Reason: Charges in a conductor reside only in its surface.

17. Assertion: Resistance of a conductor is independent of voltage.

Reason: on increasing voltage, The current also increases that is current and voltage are proportional to each other

18. Assertion: A series resonant circuit is called an acceptor circuit.

Reason: At resonant frequency, Current is maximum.

[Section - B]

19. Explain Ohms law.

20. What are equipotential surfaces? Draw equipotential surface due to a point charge.

21. What is nuclear fusion? Write one example.

22. Why two magnetic field lines cannot cross each other.

23. What are electric field lines? Draw these for a point charge-Q.

24. Why the resistance of a PN junction is low when forward biased and high when it is reverse biased?

25. Explain the difference between conductor and semiconductor.

[Section - C]

26. How are P and N type Semiconductors are formed? Name the majority charge carriers in them. Draw the energy band diagram of Pand N type semiconductor.

27. What are the functions of the control rods and moderator?

Explain nuclear fission with example.

28. Distinguish between step up and step down transformer.

29. State and explain Amperes circuital law

30. State and explain Biot Savarts law.

[Section - D]

Do any three:

31. What are rectifiers ? On what principal does it work? Explain the working of full wave rectifier. 32. Explain magnification of a compound microscope with labelled diagram.

32. Explain magnification of a compound.

33. Explain Astronomical telescope with labelled diagram.

34. Write the principle of moving coil Galvanometer. How is it converted into an ammeter? Write expression for its current sensitivity.

35. State and explain electric field intensity due to a short dipole.

[Section - E]

Case Study (1)

36. A semiconductor diode is basically a PN junction with metallic contacts provided at the end for the application of an external voltage. It is a two terminal device. When an external voltage is applied across a semiconductor diode such that P side is connected to the positive terminal of the battery and n side is connected to the negative terminal of the battery. It is said to be forward biased if the terminals are opposite, then it is reversed Biased In forward biased, conductivity is high and resistance is low and in reverse biased conductivity is low and resistance is high.

Answer the following questions:

1) Under what conditions does a junction diode work as an open switch?

2) How is forward biased different from reverse biased in a pn-junction.

3) Draw a symbol of PN junction diode.

4) What is PN junction?

Case Study (2):

37. Electric field strength is proportional to the density of lines of force that is electric field Strength at a point is proportional to the number of lines of force cutting a unit area element placed normal to the field at that point as illustrated in a given figure, the electric field at P is stronger Than at Q.

Answer the following questions:

1) What is electric field?

2) What are the direction of electric field lines?

3) What are the Sl unit of electric charge?

4) What is the dimensional formula of electric field?