Physics Viva Questions PDF

Important Viva Questions on Experiments 1. To determine resistivity of two / three wires by plotting a graph for potential difference versus current. 1) Define Ohm’s law. Answer. The current that flows through most conductors is directly proportional to the voltage applied. The voltage across a con...

Important Viva Questions on Experiments 1. To determine resistivity of two / three wires by plotting a graph for potential difference versus current. 1) Define Ohm’s law. Answer. The current that flows through most conductors is directly proportional to the voltage applied. The voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant. 2) What is the formula of Ohm’s law? Answer. Ohm’s law is given by the formula: V=IR Where, I= Current, V= Volatge, and R=Resistance. 3) What is specific resistance? Answer. The resistance offered per unit length and unit cross-sectional area when a known amount of voltage is applied is known as the specific resistance. 4) What is the SI unit of the potential difference? Answer. The SI unit of the potential difference is volt. 5) The current is measured in which unit? Answer. The unit of electric current is Ampere. 6) What is the unit of resistance? Answer. The unit of the electrical resistance is Ohms. 7) Does the resistance depend on the temperature? Answer. Yes, the resistance depends on the temperature. As the temperature increases, the resistance also increases. 8) What are the various sources of error while performing this experiment? Answer: Various sources of error are:  The instrument screws may be loose.  Lack of thick connecting wires.  Using rheostat of high resistance.  9) What is electrical conductivity? Answer. It is the measure of the ability of the material to allow the electric current to pass through it. 10) Define a rheostat. Answer. A rheostat is a two-terminal electrical device. The rheostat is a variable resistor whose resistance can be changed to change the current flowing amount through a circuit. 11) State true or false: The potential difference across the wire varies linearly with the current. Answer. TRUE. The potential difference across the wire varies linearly with the current. 12) Does the resistance depend on the dimensions of the conductor? Answer. Yes, the resistance depends on the dimensions of the conductor. 2. To find resistance of a given wire / standard resistor using metre bridge. 1) What is meant by Ohm’s law? Ohm’s law defines that the current across a conductor between two given points is directly proportional to the voltage between the two points. V/I = constant 2) What is meant by specific resistance or resistivity? Specific resistance or resistivity is the resistance of one-metre length wire and the cross-sectional area m2. 3) What is the difference between potential difference and emf? The potential difference is the work done in displacing a unit charge from one point to another. Emf is the potential difference among the terminals of a cell when no current is extracted from it. 4) Why is a connecting wire thick and enveloped with cotton thread? Thick copper wires only possess negligible resistance, and covering them with cotton helps to avoid short- circuiting. 5) What is the SI unit of resistivity? Ohm-metre or Ωm is the SI unit resistivity. 6) What is the wire material used in a rheostat? Constantan or manganin is the material of wire used in a rheostat. 7) How can we convert a galvanometer into (a) voltmeter (b) ammeter? (a) By linking a high resistance in series. (b) By linking a low resistance in parallel. 8) What is the influence of temperature on resistance? Wire resistance increases with temperature. 9) Can we consider Ohm’s law as a universal law? No, Ohm’s law is not a universal law. It totally fails on semiconductor materials and for resistances at extremely low temperatures. 10) What happens when the voltmeter is linked in series in a circuit? A voltmeter is a device used for measuring the potential difference across two points. So, the voltmeter is linked between the two points. Furthermore, the voltmeter has a high resistance, and therefore, the current in the circuit is drastically reduced. 11) What is meant by superconductivity? In specific materials, the resistance completely vanishes below a distinct temperature. This is called superconductivity. 3. To verify the laws of combination (series) of resistances using a metre bridge. 1) What is a metre bridge? A slide wire bridge, also termed a metre bridge, is an instrument that works on the principal Wheatstone bridge. To find unknown resistance of a conductor, a metre bridge is used. 2) In a series combination of resistance, how do you find the equivalent resistance? Since the same current passes through each resistor in series combination, the total resistance RT can be calculated using the below equation: RT = R1 + R2 + R3 + …….Rn 3) What is Wheatstone bridge? A Wheatstone bridge is a particular type of electrical circuit that is used in measuring the unknown electrical resistance of the circuit by balancing the two legs of the bridge circuit, where the unknown component includes one of its legs. 4) What is the use of a metre bridge? To measure the resistance precisely for a resistor, a metre bridge is used. 5) Which principle is followed by the metre bridge for its working? The principle of the Wheatstone bridge is followed by a metre bridge for its efficient working. 6) Which material wire is used in a metre bridge? The materials such as nichrome, constantan or manganin are used in making the wire of a metre bridge because these materials have a high value of resistance, and the coefficient of the temperature of their resistances is low. 7) What is the case when the metre bridge is in a more sensitive condition? The metre bridge circuit will be very sensitive when all four resistors have the same resistance values. 8) What is the balanced condition of a Wheatstone bridge? When no current flows through the galvanometer, the Wheatstone bridge is said to be in a balanced condition. By adjusting the known resistance and variable resistance, this condition can be achieved. 9) What is the working principle of a Wheatstone bridge? It is the principle of null deflection which is responsible for the working of a Wheatstone bridge, i.e. no current flows through the circuit, and the ratio of their resistances are equal. 10) What are the restrictions of Wheatstone bridge? The resistance of the leads and contacts becomes important for low resistance measurement, but the Wheatstone bridge shows errors while measuring them. 4. To determine resistance of a galvanometer by half-deflection method and to find its figure of merit. 1. What is a galvanometer? Answer: A galvanometer is a measuring device that measures a small electrical current or a function of the current by deflection of a moving coil. 2. What is the formula to calculate the figure of merit of the galvanometer? Answer: The formula to calculate the figure of merit of the galvanometer is 𝐸 𝑘= (𝑅 + 𝐺)𝜃. 3. What is an ammeter? Answer. An ammeter is a measuring instrument used to calculate the current in a circuit. 4. What is the unit to measure electric current? Answer: Ampere is the unit used to measure the electric current. 6. Define ampere. Answer: An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor. 7. How is a galvanometer converted to an ammeter? Answer: A galvanometer is converted into an ammeter by connecting a low resistance in parallel with the galvanometer. 8. On the galvanometer scale, why is zero placed in the middle? Answer: Zero is placed in the middle of the galvanometer since the galvanometer needle can deflect on both sides. 9. How is an ammeter connected in a circuit? Answer: An ammeter should be connected in the series pattern with the circuit. When the ammeter is placed in series, the entire current of the circuit can be calculated when it passes through it. 10. Why is this method known as the half deflection method? Answer: Here, the deflection is made half using a shunt resistance S. Hence It is known as the half deflection method. 11. Are there positive and negative terminals in the galvanometer? Answer: There are no positive and negative terminals in the galvanometer. 5. To find the focal length of a convex mirror, using a convex lens. 1. What is a convex mirror? Answer: A convex mirror is defined as a spherical mirror that features an outwardly bulged reflecting surface. 2. What is a convex lens? Answer: A convex lens is a type of lens that is thicker at the centre and thinner at the edges. It converges on a straight beam of light. 3. What is the formula for finding the focal length of the convex lens? Answer: The formula to find the focal length of the convex lens is 1/f=1/u+1/v. 4. Explain the type of image formed by the convex mirror. Answer: A convex mirror always creates only virtual images that are erect and diminished for all object positions. 5. What kind of image is created by the convex lens? Answer: The convex lenses form real as well as inverted images of different sizes. Erect, virtual, and enlarged images are formed based on the object’s position. 6. Is the focal length of a convex lens positive or negative? Answer: A convex lens has a positive focal length. 7. What is a convex lens referred to as? Answer: A convex lens is also referred to as a converging lens. 8. Which type of lens has a negative focal length? Answer: The concave lens is the lens which has a negative focal length. 9. Define the power of the lens. Answer: The power of a lens is defined as the reciprocal of the focal length. 10. How is the lens power measured? Answer: Lens power is measured in dioptres (D). 11. A convex lens is used to treat which type of refractive error in the human eye? Answer: The convex lens is used to treat hypermetropia or long-sightedness. 12. Why is a convex lens used in cameras? Answer: A convex lens is used in cameras because it focuses light in order to create a clear and sharp image. 13. What are the types of mirrors? Answer: Types of mirrors are,  Plane mirrors  Spherical mirrors 14. Define focal length. Answer: Focal length is the distance between the optical centre and the principal focus of the lens. 15. Is a convex mirror a transparent or opaque object? Answer: A convex mirror is an opaque object. 16. What happens to the incident ray, which is an incident on a convex lens? Answer: A convex lens converges the incident rays towards the principal axis. 17. Which lens is known as a diverging lens? Answer: A concave lens is known as a diverging lens. 18. When a concave lens is combined with a convex lens, what would be the quality of the image? Answer: A sharper image is formed when a concave lens is combined with a convex lens. 19. The lens works on which principle? Answer: The lens works on the principles of refraction. 20. Which type of lens is used in the human eye? Answer: Convex lenses are the lenses used in the human eye. 6. To find the focal length of a convex lens by plotting graphs between u and v or between 1/u and 1/v. 1) What is an optical aberration? The property of the lens that causes blurriness or distortion during the formation of an image is known as an optical aberration. The light is spread out or dispersed due to optical aberration rather than being focused on a certain fixed point. Optical aberration is an unwanted property of the lens, and by using a grouping of lenses rather than using a single piece of the lens, it can be eliminated. 2) What is magnification? Magnification of the lens is basically the ratio of the linear size of the image to the linear size of the object. m = (linear size of the image/linear size of the object) 3) What is a convex lens? A lens that is curved outwards is known as a convex lens. Convex lenses are also known as converging lenses. The thickness at the centre of a convex lens is more than its edge. A convex lens has the capability to converge a parallel beam of light into a point. 4) What is a concave lens? The type of lens with at least one side curved inwards is known as a concave lens. A Biconcave lens is a concave lens with both sides curved inward. Concave lenses are also known as diverging lenses because they spread out or diverge the rays of light that are refracted through it. 5) Define the power of a lens? The measure of the ability of a lens to converge or diverge the incident beam of light is known as the power of a lens. It is given by the reciprocal of focal length. 6) What is chromatic aberration? Dispersion is the reason why chromatic aberration occurs. Due to chromatic aberration, a lens fails to focus all colours on the same point, and colourful fringes around an image can be observed due to chromatic aberration. An achromatic doublet can be used to fix chromatic aberration. 7) Define refraction. Refraction is basically the bending of light when it passes from one medium to another. Several devices, like microscopes, corrective lenses, magnifying lenses etc., use this property of refraction. In this property, the polarisation of electrons takes place when the light is transmitted through a medium, which in turn decreases the speed of light; therefore, the direction of light changes. 8) What is total internal reflection? When the light rays travel from a more optically denser medium to a less optically denser medium, the phenomenon that happens is known as total internal reflection. 9) What are optics, and what are their types? The study of the wave properties of light is known as optics, and it is divided into three categories:  Diffraction   Interference  Polarisation 10) What is wave optics in physics? The branch of optics that studies the phenomena for which the ray calculation of geometric optics is not valid, like interference, diffraction, polarisation, and others, is known as wave optics 7. To determine angle of minimum deviation for a given prism by plotting a graph between angle of incidence and angle of deviation. 1) What are the materials required for this experiment? The materials required for this experiment are a drawing board, a white sheet of paper, a prism, drawing pins, a pencil, a half-metre scale, office pins, a protractor, and graph paper. 2) What is the theory behind this experiment? Refraction happens when a light ray moves through two adjacent mediums with different refractive indices or densities. This results in the deviation of the emergent light ray compared to the incident light ray. 3) What is a prism? A prism is a transparent optical device with polished, flat surfaces that refract light. At least one of its surfaces must be angled. A similar optical device with two parallel sides is not a prism. 4) How many edges are there in a prism? There are nine edges in a prism. 5) What is meant by the angle of deviation? The angle of deviation is the angle at which a light ray turns away from the original way while moving through a prism. 6) What are the factors that control the angle of deviation? It depends on, The angle of incidence. The material of the prism. The refracting angle (prism). The wavelength of the light used (colour). 7) What is the angle of minimum deviation? The minimum value of the deviation angle is called the angle of minimum deviation. 8) What is the importance of minimum deviation? At the condition of minimum deviation, light beams move inside the prism parallel to the prism’s base, and the angle of emergence is equal to the angle of incidence. 9) Does the colour of light influence the angle of minimum deviation? Yes, it is varied for different wavelengths or colours. 10) Which word is used as the abbreviation for remembering the names of seven colours in white light? VIBGYOR is the word used for remembering the names of seven colours in white light. 11) What is the full form of VIBGYOR? The full form of VIBGYOR is, Violet Indigo Blue Green Yellow Orange Red. 12) What is meant by the dispersion of light? The process of splitting pure white light into its seven constituent colours is known as the dispersion of light. 13) What is the conclusion of the graph of ‘i’ and ‘D’? The deviation is minimum only at one special value of incidence angle. 14) Why are there dual values of incidence angle for one particular value of deviation angle? In the case where an emergent light ray is reversed, then the angle i changes to e and the angle e changes to i. The reversed light ray will possess the exact deviation as before. 15) Does a ray of white light produce a spectrum on travelling through a hollow prism? No, dispersion does not happen in the air. For the generation of the ideal spectrum, light needs a perfect prism. 16) Which colour deviates the least? Red colour deviates the least. 17) Which colour deviates the most? Violet colour deviates the most. 18) Which colour possesses the highest refractive index? Violet colour has the highest refractive index. 19) Which colour has the lowest refractive index? Red colour possesses the lowest refractive index. 20) What is the Cauchy relation? The Cauchy relation is the connection between the wavelength of light and the refractive index of the given transparent medium. 21) What is the dispersive power of a prism? A prism’s dispersive power is the ratio of the angular dispersion for the given two colours to the average deviation generated by the prism. 22) What is the factor that controls dispersive power? Dispersive power depends on the refractive index of the prism’s material. 8. To draw the I-V characteristic curve for a p-n junction diode in forward and reverse bias. 1) What are the materials required for this experiment? A P-N junction diode, 50-volt battery, one 3-volt battery, one 0-3 volt voltmeter, one a high resistance rheostat, one 0-100 μA ammeter, one 0-50 volt voltmeter, one 0-100 mA ammeter, connecting wires, one-way key, and sandpaper are the materials required for this experiment. 2) Give three main precautions that should be taken while doing this experiment. The connections must be clean, right, and neat. A key must be used while the circuit is active. After the breakdown, voltage (forward bias) must not be provided. 3) What are the three types of materials based on electrical conductivity? Conductors, insulators, and semiconductors are the three types of materials based on electrical conductivity. 4) What is electrical conductivity? Electrical conductivity is a measure of how smoothly a body allows current to move through it. 5) What is the relationship between resistivity and electrical conductivity? The electrical conductivity of the material is reciprocal to resistivity. 6) What is a hole in the context of a semiconductor? A hole is a place in the crystal lattice of a material which is vacated by an electron. It is considered a positive charge. 7) What is an intrinsic semiconductor? An intrinsic semiconductor is a pure semiconductor that does not possess any significant dopant species. It is also called an i-type semiconductor or undoped semiconductor. 8) What is an extrinsic semiconductor? An extrinsic semiconductor is an impure semiconductor that possesses significant dopant species. 9) What is an n-type semiconductor? An n-type semiconductor is a type of intrinsic semiconductor doped using arsenic (As), antimony (Sb) or phosphorus (P) as an impurity. 10) What is meant by doping? Doping is the process of deliberately adding appropriate impurities to pure semiconductors. 11) What is meant by a junction? A junction is a common surface of p-type and n-type semiconductors. 12) What is meant by a junction potential barrier? A junction potential barrier is a potential difference between junction terminals of semiconductors. 13) What are the two types of biasing? Forward biasing and reverse biasing are the two types of biasing