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.
    Two small identical metallic balls having charges \( q \) and \( -2q \) are kept far at a separation \( r \). They are brought in contact and then separated at distance \( \frac{r}{2} \). Compared to the initial force \( F \), they will now:

      • attract with a force \( \frac{F}{2} \)
      • repel with a force \( \frac{F}{2} \)
      • repel with a force \( F \)
      • attract with a force \( F \)

    • 2.
      Assertion (A) : All atoms have a net magnetic moment. Reason (R) : A current loop does not always behave as a magnetic dipole.

        • Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
        • Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
        • Assertion (A) is true, but Reason (R) is false.
        • Both Assertion (A) and Reason (R) are false.

      • 3.
        If Bohr’s quantization postulate (angular momentum \( = \frac{nh}{2\pi} \)) is a basic law of nature, it should be equally valid for the case of planetary motion also. Why, then, do we never speak of quantization of orbits of planets around the Sun? Explain.


          • 4.
            Write the expression for the magnetic field due to a current element in vector form. Consider a 1 cm segment of a wire, centered at the origin, carrying a current of 10 A in positive x-direction. Calculate the magnetic field \( \mathbf{B} \) at a point \( (1 \, \text{m}, 1 \, \text{m}, 0) \).


              • 5.
                Write any two features of nuclear forces.


                  • 6.
                    Photoemission of electrons occurs from a metal (\( \phi_0 = 1.96 \, \text{eV} \)) when light of frequency \( 6.4 \times 10^{14} \, \text{Hz} \) is incident on it. Calculate: Energy of a photon in the incident light, The maximum kinetic energy of the emitted electrons, and The stopping potential.

                      CBSE CLASS XII Previous Year Papers

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