UNITS OF RESISTIVITY - Calculate the resistance of 100cm length of wire having a uniform cross-sectional area of 0.1mm^2 if the wire is made of manganin having a resistivity of 50x10^8 ohms-m. if the wire is drawn out to three times its original length, by how many times would you expect its resistance to be increased? Ans(500ohms; 9 times) Need solution, please help...

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anonymous · Answer

I can give you a hint. Its a very easy question. You can find the resistance by formula R = (resistivity) x (Length along which current is being propagated/Area of cross section which is perpendicular to the flow of current). SO for first part simply apply the formula and you will get the answer. For 2nd part use a very simple concept of total volume balance. Your volume is constant, so (length x Area of cross section) = C = (newLength x Area of Cross section). Now get your new area of cross section, now you can get new resistance and hence the ratio of new to old resistance.