A 13 Volt battery has an internal resistance of R1 = 50mΩ. Two lights,
in parallel, each have R2 = 10Ω of resistance. What is the voltage across the lights?
An engine is hooked up parallel to the lights, drawing a current of 40 Amps. What is
the new voltage across the lights? Diagram below shows circuit without (left) and with
(right) engine