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Resistance and Resistivity The materials can be classified as conductors, semiconductors and insulators depending on their resistivities, in an increasing order of their values. Metals have low resistivities in the range of `10^(-8)Omegam` to `10^(-6)Omegam`. At the other end are insulators like ceramic, rubber and plastics having resistivities `10^(18)` times greater than metals or more. In between these two are the semiconductors. These however, have resistivities characteristically decreasing with a rise in temperature. The resistivities of semiconductors can be decreased by adding small amount of suitable impurities. This last feature is exploited in use of semiconductors for electronic devices.Commercially produced

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EMF of a CellAn electric cell is a source of energy that maintains a continuous flow of charge in a circuit. It changes chemical energy into electrical energy. It has two electrodes, positive electrode and negative electrode as shown below.Electric cell has to do some work in maintaining the current through a circuit. The work done by the cell in moving unit positive charge through the whole circuit (including the cell) is called the electromotive force (emf) of the cell. The current flowing in the cell

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Wheatstone Bridge In 1845 by German physicist Gustav Kirchhoff described Kirchhoff’s circuit laws which are two equalities that deal with the current and potential difference (commonly known as voltage) in the lumped element model of electrical circuits.As an application of these laws, consider the circuit shown below, which is called the Wheatstone bridge. This bridge consists of four resistors `R_1, R_2, R_3 and R_4`. Across one pair of diagonally opposite points (A and C in the figure) a source is connected.This (i.e., AC) is called the battery arm. Between the other two vertices, B and Z), a galvanometer G (which

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Which of the following statement(s) is/are

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Amongst the following physical parameter, which is equivalent to

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Suppose while sitting in a parked car, you notice a jogger approaching towards you in the side view mirror of R = 2 m. If the jogger is running at a speed of 5 m s–1, how fast the image of the jogger appear to move when the jogger is

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The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm. Its focal length is 12 cm. What is the refractive index of

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An object of size 3.0cm is placed 14cm in front of a concave lens of focal length 21cm. Describe the image produced by the lens. What happens if the object is moved further away from the

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A person with a normal near point (25cm) using a compound microscope with objective of focal length 8.0 mm and an eyepiece of focal length 2.5cm can bring an object placed at 9.0mm from the objective in sharp focus. What is the separation between the two lenses? Calculate the magnifying power of the

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Explain: Why must both the objective and the eyepiece of a compound microscope have short focal

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An angular magnification (magnifying power) of 30X is desired using an objective of focal length 1.25cm and an eyepiece of focal length 5cm. How will you set up the compound

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A small telescope has an objective lens of focal length 140cm and an eyepiece of focal length 5.0cm. What is the magnifying power of the telescope for viewing distant objects when (i)For the telescope described in Exercise 34 (a), what is the separation between the objective lens and the

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Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism AB C. The refractive indices of the glass prism for the two rays 1 and 2 are respectively 1.35 and 1.45. Trace the path of these rays after entering through the prism.

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Trace the path of a ray of light passing through a glass prism ABC as shown in the figure. If the refractive index of glass is `sqrt3`, then find out the value of the angle of emergence from the

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A converging lens has a focal length of 20 cm in air. It is made of a material of refractive index 1.6. It is immersed in a liquid of refractive index 1.3. Calculate its new focal

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A convex lens is used to obtain a magnified image of an object on a screen 10 cm from the lens. If the magnification is 19, find the focal length of the

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A myopic adult has a far point at 0.1 m. His power of accomodation is 4 diopters. What is his near point without

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In a double-slit experiment the angular width of a fringe is found to be 0.2° on a screen placed 1 m away. The wavelength of light used is 600 nm. What will be the angular width of the fringe if the entire experimental apparatus is immersed in water? Take refractive index of water to be

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Let us list some of the factors, which could possibly influence the speed of wave propagation: (i) nature of the source. (ii) direction of propagation. (iii) motion of the source and/or observer. (iv) wavelength. (v) intensity of the wave. On which of these factors, if any,

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When light travels from a rarer to a denser medium, the speed decreases. Does this decrease in speed imply a decrease in the energy carried by the light wave? Justify your

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