Calculate the length of a nichrome spiral for an electric hot plate capable of heating 21 g of water to the boiling point in 8 min. The initial temperature of water is `20^@C,` the efficiency is 60%, the diameter of the wire is 0.8 mm, the voltage is 220 V. the resistivity of nichrome is `10^(-4)` ohm-m. Neglect the heat required to heal the kettle.

Answer

`9.6m`

Explanation

The length of the wire is `=(0 .6pi U^2 d^2)/(4p m_(c) triangle T)` .