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END TERM EXAMINATION
[DECEMBER 2013 -JANUARY 2014]
FIRST SEMESTER BCA
Subject Code: BCA-109

## Subject: Physics

Time: 3 Hrs M.M: 75

Note: Attempt any five questions. Question 1 is compulsory. Select one question from each unit.

Question 1: (2.5 ✕ 10 = 25)
a) If a body is not at rest then the net force acting on it can not be zero. Is this statement true or false? Justify your answer.

b) A man raises a body of mass 10 kg through a height of 2 meters. Find the work done against the force of gravity. Take g: 10 m/s²

c) Define the SI unit of power. Give its relationship with one horse power.

d) Explain how friction helps in walking.

e) Define Gauss's Law in Electrostatics. Explain briefly.

f) Define intensity of electric field at a point, Write its SI unit.

g) Explain briefly the principle of a capacitor.

h) What is a Wheatstone bridge? Draw a circuit diagram to briefly explain it.

i) What are energy bands in solids? Explain briefly.

j) What are extrinsic semiconductors? Name the minority carriers in p- type semiconductors.

UNIT-I

Question 2: (5 + 4 + 3.5 = 12.5)
a) Define Newton's first two laws. Show that the first law can be obtained from the second law.

b) A force of 10 N acts on a body of mass 200 g. Find the acceleration produced in the body.

c) Define momentum. Write its SI unit. Is it a vector quantity or a scalar quantity?

Question 3: (4 + 4 + 4.5 = 12.5)
a) Differentiate between static and kinetic friction.
b) Static friction is a self adjusting force. Explain.
c) A horizontal force of 490 N is required to slide a sledge weighing 600 kgf over a flat surface.Calculate the coefficient of friction.

UNIT-II

Question 4: (3 + 5 + 4.5 = 12.5)
a) Define work and its SI unit. What is the meaning of negative work? Briefly explain.

b) Write the expression.for the potential energy of a compressed spring. Explain the
various terms.

c) Write the names of different forms of energy. Explain the law of conservation of energy.

Question 5: (5 + 7.5 = 12.5)
a) Explain elastic and inelastic collisions. Give main differences.

b) Two identical bodies each of mass M moving with speeds U1, and U2 along a a straight line undergo a head on perfect inelastic collision. Calculate the loss in kinetic energy.

UNIT III

Question 6: (3 + 4.5 + 5 = 12.5)
a) Explain briefly frictional electricity.

b) Find the force between two stationary charges each 600 micro Coulomb kept 2 meters apart in
vacuum. How will the force vary if the charges are kept in a medium of dielectric constant 80?

c) Use Gauss's law to show that the electric field inside a charged solid conducting sphere is zero.

Question 7: (3 + 3.5 + 6 =12.5)

a) The total resistance of two resistors when connected in series is 9 Ώ and when connected in
parallel, their total resistance becomes 2 Ώ. Find the value of each resistance.

b) Define Ohm's law. Is it a fundamental law? Explain briefly.

c) State Kirchhoff rules. Explain with the help of a circuit diagram.

UNIT-IV

Question 8: (5 + 3 + 4.5 =12.5)

a) Explain briefly the basis of Rutherford's atomic model.
b) Why is the density of an atom less than the density of its nucleus? Explain briefly.
c) State the postulates of Bohr's atomic model.

Question 9: (5 + 3.5 + 4 = 12.5)
a) What is a p-n junction? Explain briefly how potential barrier is caused in it.
b) In a transistor, base is made thin and lightly doped. Why?
c) List the advantages of integrated circuits over conventional circuits.