Problema Solution

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Inverse Proportion

The resistance R of a wire of a constant length is inversely proportional to the square of its diameter d. If the resistance of a wire 2 mm in diameter is 25 ohms, find

a) an equation connecting the resistance of the wire, R, to the diameter of the wire,d.

b) the resistance of a wire with diameter 2.5 mm

c) the diameter of a wire with a resistance of 15 ohms.

Answer provided by our tutors

R = k/d2

R=25 , d=2

25 = k / 4

k=100

a) Equation :   R = 100/d2 

b) R = 100/2.52 = 16

c) 15 = 100/d2

   d = sqrt ( 100/15) = 2.58 mm