What's the formula for 2/3/4 parallel resistors?
Formula for 2 parallel resistors R1 and R2:
$$R_{total} = \frac{1}{\frac{1}{R_1} + \frac{1}{R_2}}$$Python code:
rtotal = 1. / (1./r1 + 1./r2)
Formula for 3 parallel resistors R1 and R2:
$$R_{total} = \frac{1}{\frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3}}$$Python code:
rtotal = 1. / (1./r1 + 1./r2 + 1./r3)
Formula for 4 parallel resistors R1 and R2:
$$R_{total} = \frac{1}{\frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + \frac{1}{R_4}}$$Python code:
rtotal = 1. / (1./r1 + 1./r2 + 1./r3 + 1./r4)