# A block of carbon is 2.3 cm long and has a square cross-sectional area with sides of 2.1 cm . A potential difference 8.7 V is maintained across its length. What is the resistance of the resistor?

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The resistivity of carbon is 6.5 × 10−5 Ω · m .

Answer in units of mΩ

The resistivity of carbon is 6.5 × 10−5 Ω · m .

Answer in units of mΩ

##### 1 Answer

Mar 16, 2018

Good one . See below

#### Explanation:

Firstly Resistance in milli ohmsof a material is:

where

In your case you have:

This would be the case if there was no current flow.

Applying the voltage causes a 8.7V . means there is current of: