Physics engineering viva questions
Viva questions physics practical 1st year
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1.
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Q1. Why is a spherometer so called?
A1. It measures radius of curvature of spherical surfaces, hence it is called a spherometer.
Q2.Describe principle of a spherometer.
A2.Its works on the principle of micrometer screw.
Q3. What is means by pitch of spherometer?
A3. The pitch is the distance between two consecutive threads of the screw taken parallel to the axis of rotation or the
distance moved by the screw in one complete rotation of the circular scale.
Q4.How can the accuracy of a spherometer be increased?
A4. Smaller is the L.C. is the accuracy of an instrument and vice –versa .The accuracy of the spherometer can be
increased by decreasing the pitch or by increasing the number of division of circular scale.
Q5. Can you measure the focal length of a lens?
A5.Yes.
Q6. Why are the good spherometer made of gun metal?
A6. To minimize wear and tear.
Q7.Define pitch of a spherometer?
A7.Pitch of Spherometer is linear distance moved by its screw when the circular scale is given one complete rotation.
Q8.What is value of pitch of a common spherometer?
A8. Generally it is 1mm.
Q9. What is least count of spherometer?
A9.It is liner distance moved by the screw when it is rotated by one division of circular scale only.
Q10.The spherometer contains three legs, why?
A10. Because it is the minimum number for stable equilibrium of the instrument .Moreover ,at least three points are essential to describe a plane.
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2.
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Q1. What is simple pendulum?
Ans . A simple pendulum is a heavy, small metallic bob suspended by a weightless, inextensible thread from a rigid
support point, about which it can vibrate.
Q2.Which force is responsible for vibration of a simple pendulum?
Ans.The force of gravity.
Q3. What is gravity?
A3. The force experienced by bodies situated on or near the surface of earth due to the gravitational attraction of earth.
Q4.What is value of acceleration due to gravity?
A4.g=9.8 m/s2
Q5.How g and G are correlated?
A5. g=GM/R
2
M=MASS OF EARTH, R –Radius of Earth
Q6.What should be the quality of pendulum bob for determining value of g?
A6 . Pendulum mass should be small in size ,heavy and perfectly spherical so that it may be considered as a point mass
and centre of sphere may be taken as its centre of mass.
Q7.Why does oscillating pendulum stop vibrating after some time?
A7. Due to viscous force of air.
Q8.Value of g at surface of earth is 9.81 m/sec2 , how g will varies with height and depth of earth?
A8. It’s value decreases .
Q9.What is value of g in moon with respect to earth?
A9 . Value of g is 1/6
th in moon compared to earth.
Q10 .Does time period of a pendulum depend upon the mass of bob?
A10. No.
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3.
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Q1.What is elasticity?
A1. The property of the body by virtue of which it tends to regain its original configuration when external deforming forces
acting on it are removed.
Q2. Define stress.
A2 stress is defined as the internal restoring force per unit area developed in a body when it is deformed by applying
external force.
Q3.What is strain?
A3. Strain caused in a body is defined as the ratio of change in a dimension of the body to the original dimension of the
body
Q4.What is elastic limit?
A4. Up to which the body behaves as perfectly elastic and on removing the deforming force the body regains its original
configuration completely.
Q5.What happens if a metal wire is loaded even beyond its elastic limit?
A5 Beyond elastic limit
(I) the elongation of wire is not directly proportional to the load
(ii) the wire does not regain its original state completely even on removal of the load.
Q6 would you prefer short wire or long wire in Searle’s apparatus?
A6 Long wires.
Q7. State Hooke’s law.
A7 .Within elastic limit stress is proportional to strain.
Q8. State Hooke’s law.
A8 .Within elastic limit stress is proportional to strain.
Q9.Why is a fixed weight suspended from the compensating wire of Searle’s apparatus?
A9. A fixed weight is suspended from the lower end of compensating wire frame so as to keep the wire in taut poison.
Q10. Which is more elastic, steel or rubber? Why?
A10. Steel is more elastic than rubber because for a given strain much larger stress is developed in a steel wire.
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4.
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Q1.What is surface Tension?
A1. a property of liquids due to which a free surface behaves like a stretched membrane and tends to acquire least
possible surface area.
Q2. How do you measure surface tension?
A2. Surface tension is measured by the force acting per unit length along any line taken in the free liquid film.
Q3. What is the nature of intermolecular force?
A3. Electrostatic in nature.
Q4.What is force of cohesion?
A 4 .Intermolecular force between identical molecules.
Q5.And what is force of adhesion?
A5. Intermolecular force between different molecules.
Q6.What is capillary tube?
A6. A tube with an extremely fine bore.
Q7.What is capillarity?
A7.Rise or fall of a liquid in a capillary tube as compared to the surroundings is called capillarity.
Q8.Name a liquid whose angle of contact is obtuse?
A8.Mercury.
Q9.What is angle of contact of water in contact with glass?
A9. It is practically taken as zero.
Q10.What is the cause of capillary rise of water?
A10. Existence of pressure difference across a curved water-air interface.
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5.
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Q1.What is viscosity?
A1 aproperty of fluids due to which they oppose relative motion between adjacent fluid layers.
Q2.What is the direction of viscous force?
A2Tangential to the surface but opposite to the direction of relative motion.
Q3. what is coefficient of viscosity?
A3. It is a constant for fluid and is a measure of its viscosity property.
Q4.State Stoke’s law.
A4. For a small spherical body of radius r falling down a liquid of coefficient of viscosity η , a viscous force acts whose
magnitude is F= 6π ηr v.
Q5.What is terminal velocity?
Ans.It is maximum constant velocity with which a small spherical body may fall feely trough a fluid.
Q6.On What factor terminal velocity depend?
Ans. Terminal velocity is directly proportional to the square of the radius of falling body and inversely proportional to the
coefficient of viscosity of fluid.
Q7.Do air or gases also posses the property of viscosity?
Ans. Yes, But coefficient of viscosity of gases is less than liuid.
Q8.Which is more viscous water or glycerine?
Ans . Glycerine.
Q9.What is coefficient of viscosity?
Ans.It is constant for fluid and it is measure of its viscosity property.
Q10.How does the coefficient of viscosity of a liquid change with change I temperature?
Ans. Coefficient of viscosity of a liquid rapidly decreases with increase in its temperatu
Title of the practical: To determine refractive index of the material
of prism using graph.
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6.
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Q1. What is refractive index ?
Ans. When a ray of light travels from one medium to the other medium then ratio of angle of incidence to the sine of angle
of refraction is always constant and it is called refractive index of the second medium with respect to the first medium.
Q2.on what factors the refractive index depends?
Ans. (i) Nature of the pair of media.
(II) Colour of light.
(III) Physical state of the medium and
(IV) Temparature of the medium.
Q3. What is the use of i-delta graph?
A3. This graph is used to determine angle of minimum deviation.
Q4. How is the angle of minimum deviation depends upon the colour light?
A4. It is maximum for the violet ant least for the red colour.
Q5. What is the path ray inside the prism in minimum deviation condition?
A5. Inside the prism the refracted ray is parallel to the base
Q6. Why are the good spherometer made of gun metal?
A6. To minimise waer and tear.
Q7.What is an angle of deviation?
A7:The angle between incident ray and emergent ray is called angle of deviation.
Q8.On what factors angle of deviation depends?
A8. It depends upon angle of incidence.
Q9.For which colour refractive index of the material of prism is less, red or violet?
A9 . Red.
Q10. What will happen to the refractive index if prism is cut into two equal parts?
A10. Remain same.
Q.11.Can you find refractive index of a transparent liquid by this method?
A11.Yes
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7.
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Q1. What is lens and how many types of lenses do you know?
A1. Lens is a transparent medium which is surrounded by one spherical and other plane or both spherical surfaces.
Lenses are manly of two types:
(i)convex
(II) Concave.
Subdivided Convex lens: (i) Plano-convex (ii) Double –convex (III) Concavo-convex.
Concave lens: (i) Plano-concave (ii) double-concave (III) Convexo-Concave.
Q2. What is focal length of a lens?
A2. The distance between the optical centre of the lens and its focus is called focal length.
Q3. On what factors does the focal length of a lens depend?
A3. Focal length depends upon:
Radii of curvature of the surfaces.
(i)Refractive index of the medium of lens.
(ii)Colour of rays and
(iii)Media of surroundings.
Q4. What is meant by second focus of a lens?
A4. Light rays incident on lens, parallel to its principal axis, after refraction through the lens, passes through a point or
appears to diverge from a point, this point is called the second focus.
Q5. What will be the focal length of lens of refractive index 1.5 in water?
A5. It will be 4 times of its focal length in air.
Q6. When do you get the virtual image by a convex lens?
A6. When the object is placed between the optical centre and focus.
Q7.If an object is placed at the focus of a lens where will its image form?
A7. It will formed at infinity.
Q8.What is optical centre of lens?
A8. Optical centre of a lens is that point on its principal axis where from the ray passes through undeviated.
Q9. What is difference between a convex and a Concave lens?
A9. A Convex lens is thick in its middle portion and goes on becoming thin towards its ends whereas a concave lens is
thin in its middle portion and becomes thick towards its both ends.
Q10. Can you determine the focal length of concave lens by u-v or two pin methods?
A10. No, Because a concave lens always gives virtual image
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8.
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Q1.What is rate of cooling of body?
A1. Rate of cooling of a body means rate of loss heat by it.
Q2.Who gave the law of cooling?
A2.Newton.
Q3. State Newton’s law of cooling.
A3. The rate of loss of heat by a hot body is directly proportional to the temperature difference between the hot body and
the surroundings. provided that the temperature difference is small.
Q4.What do you mean by small temperature difference?
A4.the temperature between the hot body and surroundings must be less than40 degree Centigrade
Q5.In your experiment why do you make the outer surface of calorimeter to be dull black?
A5.So that it becomes a good radiator of heat.
Q6.Why do you fill water in double walled enclosure?
A6.As specific heat capacity of water is very high. Its temperature practically remains constant in spite of the fact that is
receiving heat emitted by calorimeter.
Q7.Why do you stir the hot water continuously?
A7.So that temperature of water remains uniform through out.
Q8.What is the limitation of Newton’s law of cooling?
A8.It is true only when temperature difference between the hot body and the surroundings is small .for large temperature
difference the law fails.
Q9.What is radiation?
A9. Emission of thermal by any hot body, which can travel even through vacuum with a speed of 3x10 power 8meter per
second.
Q10.What is method of loss of heat for a body?
A10 A hot body may lose heat by conduction, convection or radiation.
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9.
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Q1. Can two magnetic lines of force intersect each other? why?
A1 No, two lines of force never intersect each other . If they intersect each other , then at the point of intersection, two
tangents can be drawn and thus we have two directions of magnetic field at that point , which is impossible.
Q2. What is neutral point?
A2 The points where net magnetic field due to the bar magnet and horizontal component of earth’s magnetic field is zero
are called neutral points.
Q3. Why is the compass needle tapped gently at the neutral point?
A3. Because, near the neutral point the field acting on the needle is very weak and not be able to overcome the force due
to friction at point of suspension.
Q4.What are the pole of a magnet?
A4 Poles of a magnet are the points where the magnetic property is maximum.
Q5.What is the poison of neutral points when North Pole of the magnet points toward geographic north or south?
A5. In this case, the neutral points are obtained on the equatorial line or broadside-on poison of the magnet for north.
In this case, the neutral points are obtained on the axial line or end side-on poison of the magnet for north.
Q6. What is magnetism?
A6. The Phenomenon of magnet attracting small piece of iron is known as magnetism.
Q7.What are the poles of a magnet?
A7. The poles are magnets are the points where the magnetic property is maximum.
Ans. A magnetic field that is constant both in magnitude and direction at every point is called uniform magnetic field.
Q.9.Why do way say that magnetic lines force are closed loops?
Ans. Because they start from N-pole of the magnet and enter at S-pole outside the magnet. wheres they move from Spole to N-pole inside the magnet.
Q.10.Can you have an isolated single pole?
Ans. No, poles of a magnet always occur in pairs
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