RBSE Class 12 Physics Model Paper 5 English Medium are part of RBSE Class 12 Physics Board Model Papers. Here we have given RBSE Class 12 Physics Sample Paper 5 English Medium.

Board |
RBSE |

Textbook |
SIERT, Rajasthan |

Class |
Class 12 |

Subject |
Physics |

Paper Set |
Model Paper 5 |

Category |
RBSE Model Papers |

## RBSE Class 12 Physics Sample Paper 5 English Medium

**Time : 3 ¼ hours**

**Total: 56 **

**General Instructions to the Examinees**

- Candidate must first his/her Roll No. on the question paper compulsorily.
- All the questions are compulsory.
- Write the answer to each question in the given answer-book only.
- For questions having more than one part, the answer to those parts are to be written together in continuity.
- If there is any error/difference/contradiction in Hindi & English version of the question

paper, the question of Hindi version should be treated valid. -
**Question Nos****Marks per Questions**1-13 1 14-24 2 25-27 3 28-30 4 - There are internal choices in Q. NOs. 21 and 27 to 30.
- Use of calculator is not allowed in the examination.

**Section – A**

Question 1.

Write down the relation between electric field and electric potential at a point.** [1]**

Question 2.

Name one material having a small value of temperature coefficient of resistance. Write one use of this material.** [1]**

Question 3.

Two thin long wires separated by a distance a carry current I amp each. What is the magnitude of the force per unit length exerted by each wire on the other?** [1]**

Question 4.

State one limitation of cyclotron.** [1]**

Question 5.

What is geographic meridian?** [1]**

Question 6.

How does self-inductance of a coil change when an iron rod is introduced in it.** [1]**

Question 7.

When light undergoes refraction, what happens to its wavelength?** [1]**

Question 8.

State de-Broglie hypothesis.** [1]**

Question 9.

Calculate the number of photons in 6.62J of radiation energy of frequency 10^{12} Hz.** [1]**

Question 10.

Define radioactive decay constant and write its unit.** [1]**

Question 11.

What is the approximate value for the voltage across depletion layer of a silicon type junction diode?** [1]**

Question 12.

Name the part of em spectrum which is used in greenhouse?** [1]**

Question 13.

What do you mean by skip distance and skip zone?** [1]**

**Section – B**

Question 14.

Calculate the electric field strength required to just support a water drop of mass 10^{-7} kg having a charge 1.6xl0^{-19}C.** [2]**

Question 15.

How internal resistance of a primary cell can be determined by a potentiometer?** [2]**

Question 16.

When a resistor of 10Ω is connected in series with a battery, the current is 0.8A. When a resistor of 20Ω is connected the current becomes 0.5A. Calculate the emf and the internal resistance of the battery. ** [2]**

Question 17.

A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12cm when the coil is in a vertical plane making an angle of 45° with the magnetic meridian. Calculate the horizontal component of the earth’s magnetic field. ** [2]**

Question 18.

A current is made up of two components: 3amp DC and an AC given by i = 4 sinωt amp. Write down the expression for current and calculate its rms value.** [2]**

Question 19.

Two sources of intensity I_{1} and I_{2} undergo interference in Young’s double slit experiment.** [2]**

Show that \(\frac{1}{I_{\min }}=\left(\frac{a_{1}+a_{2}}{a_{1}-a_{2}}\right)^{2}\) where a_{1} and a_{2} are the amplitudes of disturbances for the two sources S_{1} and S_{2}, respectively

Question 20

The image obtained with a convex lens is erect and its length is four times the length of the object. If the focal length of the lens is 20cm, calculate the object and image distances. ** [2]**

Question 21.

Find the number of photons emitted per second by a 25-watt bulb of monochromatic light of wavelength 6000A. What is the photoelectric current assuming 3% efficiency for photoelectric effect? ** [2]**

Question 22.

(a) Calculate the orbital velocity of the electron in hydrogen atom assuming its total energy to be -13.6eV and hence.

(b) Calculate frequency of revolution of the electron around the nucleus. What is the frequency of light emitted by the electron? ** [2]**

**OR**

The isotope of uranium \(_{ 92 }^{ 238 }{ U }\) decays successively to form \(_{ 90 }^{ 234 }{ Th }\), \(_{ 91 }^{ 234 }{ Pa }\), \(_{ 92 }^{ 234 }{ U }\), \(_{ 90 }^{ 230 }{ Th }\), \(_{ 88 }^{ 226 }{ Ra }\) and \(_{ 86 }^{ 222 }{ Rn }\).What are the radiations emitted in each decay process?

Question 23.

(a) Identify the semiconductor device used in breakdown region of reverse characteristics of a junction diode.

(b) Draw the circuit diagram to obtain the characteristics of that device.

(c) Briefly explain how this device is used as voltage regulator. ** [2]**

Question 24.

Prove that displacement current across a capacitor is equal to conduction current in conducting wires.** [2]**

**Section – C**

Question 25.

(a) Define binding energy of a nucleus.

(b) Plot binding energy curve and write two important conclusions from this plot.** [3]**

Question 26.

What is an amplifier? Describe a common-emitter transistor amplifier using a PNP transistor. Drive expression for current and voltage gain. Write the phase relationship between output and input signal.** [3]**

Question 27.

State Ampere’s circuital law. Apply it to find magnetic field due to a current carrying long cylindrical conductor at an external point.** [3]**

**OR**

Give the theory of moving coil galvanometer.** [3]**

**Section – D**

Question 28.

(a) Define electron-volt and write its value in Joule.

(b) Derive an expression for electric potential due to an electric dipole.

(c) A regular hexagon of side 10cm has a charge of 5pC at each of its corners. Calculate the potential at the centre of the hexagon. **[1+2+1=4]**

**OR**

(a) Define electric flux. How the flux is expressed in terms of surface integral of the electric field ?

(b) Using Gauss’ law, find an expression for electric field due to a uniformly charged thin spherical shell

- outside the shell and
- inside the shell.

(c) The electric field intensity in a region is given by \(\vec { E }\) = (2\(\widehat { j } \)+ 3\(\widehat { k } \))N / C. Calculate electric flux linked with z-x plane of a square of side 10cm.

Question 29.

(a) Write three expressions for energy stored in a capacitor.

(b) Prove that an ideal capacitor connected to an AC source does not dissipate any power. (c) Explain why the reactance of the capacitor decreases wtih increasing frequency. **[1 + 2 + 1=4]**

**OR**

(a) Define rms value of AC.

(b) Obtain an expression for rms value of AC.

(c) What time is taken by AC to attain its peak value from zero if its frequency is 50 Hz? **[1 + 2 +1=4]**

Question 30.

(a) Derive the lens makers formula for a double convex lens.

(b) State the assumption used and the sign convention used.

(c) A convex lens of focal length 0.2m, made of glass (n=1.5) is immersed in water (n=1.33). Find the change in focal length of the lens. **[2 + 1 + 1=4]**

**OR**

(a) What is a coherent source of light? Can two independent sources be coherent? **[1 + 2 + 1=4]**

(b) Describe Young’s double slit experiment and derive an expression for fringe width.

(c) The intensity of central maximum in Young’s double slit experiment is I_{0}. If the distance of a point in the direction of other maxima and minima is one-third of the fringe width. Show that intensity at that point will be I_{0}/4.

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