Find the highest and lowest total resistance of a combination of four coils with resistances 4 ohms, 8 ohms, 12 ohms, 24 ohms.

According to the question, there are four coils of resistances = 4 Ω, 8 Ω, 12 Ω and 24 Ω

  1. Given that the coils are connected in series, then equivalent resistance will have to be highest:

⇒ 4 + 8 + 12 + 24 = 48 Ω

  1. Given that the coils are connected in parallel, then equivalent resistance will have to be the lowest:

⇒ 1/R = 1/4 + 1/8 + 1/12 + 1/24

= 1/2

Therefore, R = 2 ohms can be expressed as the least value of resistance which can be obtained from the above 4 resistor combinations.


Related Questions

  1. In An Arrangement Of Resistances, Find Effective Resistance Between Points A and B.
  2. What Is Effective Resistance?
  3. What is Null Voltage?
  4. Three Incandescent Bulbs (Each 100 W) Are Attached In Series. In Another Circuit, Three More Bulbs Of Same Wattage Are Attached Parallelly To An Equal Source.
  5. Two Identical Resistors With Resistances 15 Ohm Are Connected In Series And Parallel To A Battery Of 6 V. Calculate Ratio Of Power Consumed.
  6. A Circuit Consists Of A Battery Of 3 Cells (2 V Each), A Combination Of Three Resistors, 10 Ohm, 20 Ohm And 30 Ohm, Attached Parallelly, With Plug Key And Ammeter (In Series).
  7. X and Y, which are two resistors, with resistances of 2 Ω and 3 Ω respectively are first connected in parallel and then in series. In both cases, the voltage that is supplied is 5 V. (i) Illustrate a circuit diagram to show the combination of resistors. (ii) Calculate the amount of voltage across 3 Ω resistor in the series combination of resistors.
  8. Draw An Electric Circuit With A Cell, Key, Ammeter, A Resistor (Series) Of 2 Ohm With a Combination Of Two Resistors (4 Ohm Each) In Parallel And A Voltmeter Across Parallel Combination.

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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.
      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.


        • 3.
          An astronomical telescope consists of two converging lenses. One of them of large aperture and large focal length is called objective lens and the other one, of smaller focal length and smaller aperture is called the eyepiece. It is used to see distant objects which are not seen clearly with naked eyes. The image formed by the objective lens acts as an object for the eyepiece and the final image produced by the eyepiece is magnified.


            • 4.
              Consider the nuclear reaction \( X \to Y + Z \). Let \( M_x \), \( M_y \), and \( M_z \) be the masses of the three nuclei X, Y, and Z respectively. Then which of the following relations hold true?

                • \( (M_x - M_z)<M_y \)
                • \( (M_x - M_y)<M_z \)
                • \( M_x>(M_y + M_z) \)
                • \( M_x<(M_y + M_z) \)

              • 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.
                    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.

                      CBSE CLASS XII Previous Year Papers

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