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.
    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.


      • 2.
        A light copper ring is freely suspended by a light string. A bar magnet is held horizontally with its length along the axis of the ring. The magnet is moved towards the ring with its N pole facing the loop. What will happen to the ring and its position? Explain.


          • 3.
            Four independent waves are expressed as \[ (i)\; y_1=A_1\sin\omega t, \] \[ (ii)\; y_2=A_2\sin 2\omega t, \] \[ (iii)\; y_3=A_3\cos\omega t, \] \[ (iv)\; y_4=A_4\sin\left(\omega t+\frac{\pi}{3}\right) \] The interference between two of these waves is possible in

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              • All of them

            • 4.
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                • repel with a force \( \frac{F}{2} \)
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              • 5.
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                  • 6.
                    Two parallel plate capacitors X and Y are connected in series to a 6 V battery. They have the same plate area and same plate separation but capacitor X has air between its plates, whereas capacitor Y contains a material of dielectric constant 4. Calculate the capacitances of X and Y, if the equivalent capacitance of the combination of X and Y is \( 4 \, \mu\text{F} \). Calculate the potential difference across the plates of X and Y.

                      CBSE CLASS XII Previous Year Papers

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