Define least count.

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Jasmine Grover

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Least count is a term used in measurement that refers to the smallest unit of measurement that can be made using a particular instrument. It is defined as the reciprocal of the number of divisions on the instrument's scale.

For example, if a ruler has 10 divisions for every centimeter, its least count is 1/10 cm. The least count determines the accuracy of the measurement and is an important factor in choosing the right instrument for a particular measurement task.

Least Count

The least count is the smallest value that can be measured using a measuring instrument.

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CBSE CLASS XII Related Questions

  • 1.
    Two metal spheres of radii $r_1$ and $r_2$ ($> r_1$) having charges $q_1$ and $q_2$ respectively kept in air, are brought in contact. Which of the following statements is not correct ?

      • The total charge of the two spheres is conserved.
      • Both spheres attain the same potential.
      • The final potential of the system equals $\frac{1}{4\pi\epsilon_0} \frac{(q_1 + q_2)}{(r_1 + r_2)}$
      • The final potential of the system equals $\frac{1}{4\pi\epsilon_0} \frac{(q_1 + q_2) (r_1 + r_2)}{r_1 r_2}$

    • 2.
      With the help of a labelled diagram, explain the principle, construction and working of an a.c. generator.


        • 3.
          The resistance of a metal wire at \( 20^\circ \text{C} \) is \( 1.05 \, \Omega \) and at \( 100^\circ \text{C} \) is \( 1.38 \, \Omega \). Determine the temperature coefficient of resistivity of this metal.


            • 4.
              Read the following paragraph and answer the questions that follow.
              In an experiment with convex lens of focal length f, the screen is fixed at a distance D from the object. A student slowly moves the lens away from the object towards the screen and finds that she is able to form sharp image of the object for two positions of the lens. The distance between these two positions of the lens is d.


                • 5.
                  Read the following paragraph and answer the questions that follow.
                  A p-type or n-type semiconductor can be converted into a p-n junction by doping it with suitable impurity. The motion of majority charge carriers causes diffusion current across the junction while the barrier electric field causes motion of minority carriers for drift current. In case of unbiased diode, the diffusion and drift currents are equal. This equilibrium is disturbed by the biasing batteries. Diodes, therefore, allow currents in one direction. This property of diode is used in making rectifiers.


                    • 6.
                      Derive an expression for the capacitance of a parallel plate capacitor of plate area A and plate separation d with air present between the plates.

                        CBSE CLASS XII Previous Year Papers

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