A diode in code

You will write four functions that describe a silicon diode, from the diode equation to a diode in series with a resistor.

The idea. The diode equation is $I = I_s\left(e^{V/V_T} - 1\right)$, with $V_T = \dfrac{kT}{e}$. In a circuit, a conducting silicon diode drops about $0.7$ V. The dynamic resistance is $r_d = \dfrac{V_T}{I}$.

Your tasks.

1. In thermal_voltage, return $V_T = kT/e$ in V for a temperature in K, using K_OVER_E = 8.617e-5 V/K.
2. In diode_current, return the current in A for a voltage in V, a saturation current in A and a temperature in K.
3. In series_current, return the current in A for a battery voltage, a resistance and a diode drop (default $0.7$ V).
4. In dynamic_resistance, return $r_d$ in ohm for a forward current in A and a temperature in K.