Determine the following from an electric circuit a) Effective resistance of 8 ohm resistors combination b) Flowing current via 4 ohm resistor

In order to determine the following from the electric circuit, we have to schematically represent it first.

Electric Circuit

Effective Resistance of 8-ohm Resistors Combination

There are two 8Ω resistors that are parallelly connected with one another, therefore their effective resistance equals:

⇒ 1/RP = 1/8 + 1/R

⇒ 1/RP = 1/4

⇒ RP = 4Ω

The Total Resistance in the given Circuit

As per the question, the following can be shown:

⇒ R = 4Ω + RP

⇒ R = 4Ω + 4Ω

⇒ R = 8Ω

Current Passing Via the Circuit

The current that passes through the circuit

⇒ I = V/R

⇒ I = 8/8

⇒ I = 1 A

Hence, the current that passes through a 4Ω resistor is 1A. Since 4Ω and Rp are connected in series, the same current flows through them.

Potential Difference across 4Ω resistor

⇒ V = I × R

⇒ V = 1 × 4

⇒ V = 4V

The Dissipated Power in a 4Ω Resistor

⇒ P = I2R

⇒ P = 12 × 4

⇒ P = 4 W

Difference, if any, in Ammeter Readings

Both A1 and A2 demonstrate the same reading due to the fact that current remains same in series combination.


Related Questions

  1. 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.
  2. Two Identical Resistors With Resistances 15 Ohm Are Connected In Series And Parallel To A Battery Of 6 V. Calculate Ratio Of Power Consumed.
  3. For The Resistor Combination, Find The Equivalent Resistance Between M and N.
  4. 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).
  5. In An Arrangement Of Resistances, Find Effective Resistance Between Points A and B.
  6. What Is Effective Resistance?
  7. Find The Highest And Lowest Total Resistance Of A Combination Of Four Coils With Resistances 4 Ohms, 8 Ohms, 12 Ohms, 24 Ohms.
  8. What is Null Voltage?
  9. 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.
  10. 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.
    An electric field $\vec{E}$ is established across the ends of a cylindrical conductor of length L and area of cross-section A. Discuss how electrons attain an average velocity, independent of time. Hence, obtain a relation between current in the conductor and this ‘average velocity’ of electrons.


      • 2.
        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.


          • 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.
                This ‘average velocity’ is found be few mm/s for currents in range of a few amperes. How then is current established almost the instant a circuit is closed ?


                  • 5.
                    Capacitors are manufactured with certain standard capacitances and working voltages. However, these standard values may not be the ones that are actually needed in a particular application. Two or more capacitors can be grouped in series or in parallel to achieve desired capacitance and voltage. When connected in series, the total capacitance decreases while the voltage rating increases, whereas in parallel connections, the total capacitance increases and maintains the same voltage rating. A capacitor stores energy in the electric field between its plates and stored energy is proportional to the square of the voltage and capacitance $U = \frac{1}{2}CV^2$, where symbols have their usual meanings.
                    Two capacitors, one of $3 \ \mu$F and the other of $6 \ \mu$F, are connected in series in the circuit as shown in the figure, for a long time. }


                      • 6.
                        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 $\frac{1}{4\pi\epsilon_0} \frac{(q_1 + q_2) (r_1 + r_2)}{r_1 r_2}$
                        CBSE CLASS XII Previous Year Papers

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