A wire of \(10\Omega\) resistance is stretched to thrice its original length. Assuming that there is no change in its density on stretching. Calculate: (i) Resistance. (ii) Resistivity of new wire.
Ans:(i) \(90\Omega\) and (ii) Same as Pervious.
A wire is stretched to reduce its diameter to half its original value. What will be new resistance?
Ans: \(R_{f}=16R_{i}\).
A wire has a resistance of \(16\Omega\). It is melted and drawn into a wire of half of its length. Calculate: the resistance of new wire. What is percentage change in the resistance?
Ans: \(R_{f}=4\Omega\) and \(\frac{\left(R_{f}-R_{i}\right)}{R_{i}}\times 100 = 75\%\).
A wire of resistance \(5\Omega\) is drawn out so that its length is increased by twice the original length, Calculate: the new resistance.
Ans: \(R_{f}=45\Omega\).
A copper wire is stretched to make it \(0.2%\) longer. What is the percentage change in its resistance?
Ans: \(\frac{dR}{R}\times 100=0.4\%\).
Two wires A and B of equal mass and of same metal are taken. The diameter of the wire A is half of the diameter of wire B. If resistance of wire A is \(32\Omega\), then, calculate the resistance of wire B.
Ans: \(R_{B}=2\Omega\).
A cylindrical metallic wire is stretched to increase its length by \(5%\). Calculate: the percentage change in its resistance.
Ans: \(\frac{\Delta R}{R}\times 100=10.25\%\).
On applying the same potential difference between the ends of the wires of iron and copper of same length, the same current flows through them. Compare their radii. Given: the specific resistance of iron and copper are respectively \(\left(1.0\times10^{-7}\right)\) and \(\left(1.6\times10^{-8}\right)\) \(\Omega m\). Can their current densities be made equal by taking appropriate radii?
Ans: \(\frac{r_{iron}}{r_{copper}}=2.5\).
A wire of resistance \(1\Omega\) is stretched to double of its initial length. What is the new resistance of wire?
