How do you find the resistance of a wire?

The resistance of a wire can be calculated when the cross-sectional area of the wire, its length, and the resistivity of the material are given. It can be calculated as follows – 

Resistance Formula

\(R = \rho {L \over A}\)

  • Where R refers to the resistance,
  • ρ is the resistivity of the wire,
  • L is the length of the wire and
  • A is the cross-sectional area of the wire.

Length of the wire – The greater the length of the wire, the greater its resistance
Cross-sectional area – The greater the cross-sectional area, the lesser its resistance
The resistivity of the material – The greater the resistivity, the greater the resistance


If the current and voltage in a circuit are known, then resistance can be calculated by Ohm’s law through the formula:

R = V/I

where R is the resistance, V is the voltage and I is the current.


Related Questions

  1. What is the necessary condition for a conductor to obey Ohm's Law?
  2. State Ohms law. How can it be verified experimentally?
  3. What are the 3 forms of Ohm's law
  4. What are the limitations of Ohm's Law?
  5. State Ohms Law. Express It Mathematically. Define Si Unit Of Resistance.
  6. What Is The Basic Principle Of Ohm's Law?
  7. Draw a circuit diagram to verify the ohms law.
  8. The resistance R= V/I, where V=100 ± 5.0V and I = 10 ± 0.2A. What is the total error in R?
  9. How Do You Determine The Resistance Of A Resistor?
  10. Find the current through a resistance of 2 ohms if the voltage across the resistance is 6V.
  11. Why is the series arrangement not used for domestic circuits?
  12. Obtain the equation J=σE of Ohm's law on the basis of drift velocity.
  13. An electric lamp of 100 Ohms, a toaster of resistance 50 Ohms, and a water filter of resistance 500 Ohms are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?
  14. What Is The Principle Of Rheostat?
  15. A small bulb has a resistance of 2 ohms when it is cold. It draws 0.4-ampere current from a source of4V and then starts glowing. Calculate the resistance when it is glowing

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CBSE CLASS XII Related Questions

  • 1.
    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.


      • 2.
        Two air-filled capacitors of capacitances $C_1$ and $C_2$ are connected in parallel with a dc battery. After the capacitors are fully charged, a slab of dielectric constant K is inserted between the plates of each capacitor. How will the (i) charge on each capacitor and (ii) energy stored in the capacitor affected after the slab is introduced.


          • 3.
            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 $\frac{1}{4\pi\epsilon_0} \frac{(q_1 + q_2) (r_1 + r_2)}{r_1 r_2}$

            • 4.
              Consider a cylindrical conductor of length \( l \) and area of cross-section \( A \). Current \( I \) is maintained in the conductor and electrons drift with velocity \( \vec{v}_d \, (|\vec{v}_d| = \frac{eE}{m} \tau) \), where symbols have their usual meanings. Show that the conductivity of the material of the conductor is given by \[ \sigma = \frac{n e^2 \tau}{m}. \]


                • 5.
                  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?

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

                  • 6.
                    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.

                      CBSE CLASS XII Previous Year Papers

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