A copper wire of length `1 m` and radius is joined in series with an iron wire of length `2 m` and radius `3 mm` and a current is passed through the wire. The ratio of the current density in the copper and iron wires is

A silver wire of length 2m and radius 1mm is joined in series with an iron wire of length "4m" and radius "3mm" and a current is passed through the wires. The ratio of the current density in the silver and iron wires is

The same mass of copper is drawn into two wires 2 mm and 3mm thick. The two wires are connected in series and current is passed through them. The ratio of heat produced in the two wires is

The same mass of copper is drawn into two wires 2 mm and 3mm thick. The two wires are connected in series and current is passed through them. The ratio of heat produced in the two wires is

The same mass of copper is drawn into two wires 2mm and 3mm thick,. The two wires are connected in series and current is passed through them. The ratio of heats produced in the two wires is-

The same mass of copper is drawn into two wires 2 mm and 4mm thick. The two wires are connected in series and current is passed through them. The ratio of heat produced in the two wires is

One end of a horizontal thick copper wire of length 2 L and radius 2R is welded to an end of another horizontal thin copper wire of length L and radius R. When the arrangement is stretched by applying forces at two ends, find the ratio of the elongation in the thin wire to that in the thick wire.

A current of 0.09A flows through a wire of area of crosssection 1mm^(2) . Find the current density in the wire.