The constant `A` in the Richordson-Dushman equation is `60 xx 10^4 A m^(-2) K^(-2)` for tungsten. A tungsten cathode has a total surface area of `2.0 xx 10^(-5) m^2` and operates at `2000 K`. The work function of tungsten is `4.55 eV`. Calculate the electric current due to thermionic emission.

Explanation

To calculate the electric current due to thermionic emission from a tungsten cathode using the Richardson-Dushman equation, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Richardson-Dushman Equation**:
The Richardson-Dushman equation for thermionic emission is given by:
\[
I = A \cdot S \cdot T^2 \cdot e^{-\frac{\phi}{kT}}
...