Question

A filament is light for a short period of time. Touch it. What do you feel?

Answer 1

Hint:In order to solve this question we need to understand the heat energy developed due to current and temperature difference. Heat is defined as the energy which flows due to temperature difference. Also whenever a wire is subjected to potential difference then an electric field is set up in the wire which binds the electrons to flow in opposite directions.

Complete step by step answer:
An electric current flows in the direction of applied electric field or in the direction of decreasing potential, so wire opposes this behavior and develops resistance or opposition which causes the energy flow by current to lose heat. Heat developed is directly proportional to square of current, resistance and time period.

Let us take tungsten filament for example kept in vacuum, we know whenever a current is passed through it, tungsten filament develops resistance and hence heat is generated in it but the filament is kept in vacuum so it does not catch the fire.Let “i” current passed in filament and it develops resistance “R”, so the heat generated in time “t” is, $H = {i^2}Rt$.Now if we touch the filament with bare hands for a short interval of time, then we can feel the heat but of low intensity provided current flow is less.

Note: It should be remembered that, we feel heat because there is temperature difference, since the filament is at high temperature and our hands are comparatively at lower temperature then heat flows because of temperature difference and our body senses it as hot filament. Heat transferred here by the method of radiation as no matter is exchanged in this process.