A Level Physics Practice Exam

Low internal resistance in car batteries is crucial primarily because it enables the battery to deliver large currents, which are essential for starting the engine. When the starter motor of a car is engaged, it requires a substantial amount of current—often hundreds of amperes—to initiate the engine's operation. If the internal resistance of the battery were high, it would impede the flow of current, reducing efficiency and potentially preventing the engine from starting altogether.

In a battery with low internal resistance, the voltage drop across the battery while supplying high current is minimal. This means that most of the available voltage can be utilized effectively to power the starter motor.

Additionally, while factors like overall weight, battery longevity, and size are relevant considerations in battery design, they are not the primary reasons for the importance of low internal resistance in the context of car batteries specifically. The ability to provide the necessary current efficiently is paramount when starting a vehicle.