If the temperature of a tungsten filament is raised from 2000 K to 2010 K, by what factor does the emission current change? Work function of tungsten is 4.5 eV.
According to Richardson-Dushman Equation thermionic current i is
where, n is the thermions emitted, S is the surface area, T is the absolute temperature, k is the Boltzmann constant, A is the constant depend on nature of metal and ϕ is the work function
Given,T1=2000 K
T2=2010 K , Φ =4.5 eV
Now,
Required factor is