A copper wire has a diameter of 0 . 5 mm and a resistivity of 1 . 6 × 10 - 6 ohm - cm . How much of this wire would be necessary to make a resistance of 10 ohm ?

Given, Resistivity, ρ = 1 .6 × 10 − 6 Ω cm Diameter, d = 0 . 5 mm Radius, r = d 2 = 0 . 5 2 = 0 . 25 × 10 - 1 c m Resistance, R = 10 Ω The equation for resistance is, R = ρ l A R = ρ l A = ρ l π r 2 ∴ l = R π r 2 ρ = 10 × 3 . 14 × 0 . 25 × 10 - 1 × 0 . 25 × 10 - 1 1 . 6 × 10 - 6 = 12 , 265 . 62 mm

Ohm's Law states that potential difference across a conductor is directly proportional to current flowing through conductor keeping physical factors constant. V ∝ I V = I R where R is proportionality constant and called resistance of conductor. S.I. unit of R is ohm.

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 3 - Current Electricity>Exercise>Q 11

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12th Karnataka Board

IMPORTANT

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Write down the mathematical expression of Kirchhoff's junction law?

Important Questions on Current Electricity

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12th Karnataka Board

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Physics Crash Course (Based on Revised Syllabus-2023)>Chapter 3 - Current Electricity>Exercise>Q 12

Plot a graph between the variation of current density

(j)

versus the electric field

(E)

for two conductors of different material. What information from this graph regarding the properties of conducting material, can be obtained which can be used to select suitable material foe use in making (i) standard resistance