Why do headlights on a car dim when the motor is operated

[valli]

Homework Statement

why do headlights on a car dim when the starter motor is operator.
battery emf = 12V
internal resistance - .040 ohm
starter motor current = 100 A.

Homework Equations

The Attempt at a Solution

 

[sylas]

Welcome to physicsforums, valli. I hope you find it helpful. The way we roll here is that you also give some relevant equations and your first attempt at a solution, and then someone will be along to give some guidance to get the rest of the way to a solution. Good luck!