Townsend's Procedure for Current Growth: Secondary Process

The net number of secondary electrons produced per incident positive ion, photon, excited particle, or metastable particle.

The total value of γ is the sum of the individual coefficients due to the three different processes, i.e., γ = γ1 + γ2 + γ3.

The total average current in a gap before the occurrence of breakdown.

<p>The Townsend first ionisation coefficient, denoted by α, is defined as the average number of ionizing collisions made by an electron per centimetre travel in the direction of the electric field.</p> Signup and view all the answers

<p>In Townsend's experiment, the current first increases proportionally with voltage, then remains constant at saturation current 𝐼0, and finally increases exponentially at higher voltages.</p> Signup and view all the answers

<p>The exponential increase in current is due to the ionization of gas by electron collision, and it is explained using the Townsend first ionisation coefficient α, which represents the average number of ionizing collisions made by an electron per centimetre of travel in the direction of the field.</p> Signup and view all the answers

<p>If the total energy of the positive ion is greater than twice the work function of the metal</p> Signup and view all the answers

<p>Townsend's secondary ionisation coefficient due to positive ions</p> Signup and view all the answers

<p>Electron emission from a metal surface occurs at the critical condition, where the energy supplied in the form of a photon of ultraviolet light is enough to overcome the surface potential barrier.</p> Signup and view all the answers

<p>The relationship is given by the equation h𝛾 ≥ 𝜑, where h is the Planck's constant</p> Signup and view all the answers