A potentiometer circuit has been set up for finding the internal resistance of a given cell. The main battery, used across the potentiometer wire, has an emf of 2.0 V and a negligible internal resistance. The potentiometer wire itself is 4 m long. When the resistance R, connected across the given cell, has values of (i) infinity,    (ii) 9.5 $$\Omega $$
the balancing lengths on the potentiometer wire are found to be 3 m and 2.85 m, respectively. The value of internal resistance of the cell is

Ten identical cells connected in series are needed to heat a wire of length one meter and radius 'r' by 10^oC in time 't'. How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time 't' ?

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

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?