a metal wire has diameter of 0.25 mm and electrical resistivity of 0.8×10^-8 ohm-m.
(i) what will be the length of this way to make a resistance 5 Ohm?
(ii) how much will the resistance change, if the diameter of the wire is doubled?
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R= p l /A
l = 5 × 2 × 3.14 × 0.25 × 10-³ / 0.8 × 10^-8
l = 7.85 × 10^5 / 0.8
l= 9.8125 × 10^5 m
ii ) reaistance is inversaly proportional to area so it will decrease 4 times
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