Two rods are joined end to end, as shown. Both have a cross-sectional area of 0.01 cm². Each is 1 meter long. One rod is of copper with a resistivity of 1.7 $$ \times $$ 10^$$-$$6 ohm-centimeter, the other is of iron with a resistivity of 10^$$-$$5 ohm-centimeter.

How much voltage is required to produce a current of 1 ampere in the rods?

A 12 cm wire is given a shape of a right angled triangle ABC having sides 3 cm, 4 cm and 5 cm as shown in the figure. The resistance between two ends (AB, BC, CA) of the respective sides are measuread one by one ratio

The resistances of the four arms P, Q, R and S in a Wheatstone's bridge are 10 ohm, 30 ohm, 30 ohm and 90 ohm, respectively. The e.m.f. and internal resistance of the cell are 7 volt and 5 ohm respectively. If the galvanometer resistance is 50 ohm, the current drawn from the celll will be

A wire of resistance 4 $$\Omega $$ is stretched to twice its original length. The resistance of stretched wire would be