Question

Semi-tractor trucks use four large\({\rm{12 - V}}\) batteries. The starter system requires \({\rm{24}}\;{\rm{V}}\), while normal operation of the truck’s other electrical components utilizes \({\rm{12}}\;{\rm{V}}\). How could the four batteries be connected to produce \({\rm{24}}\;{\rm{V}}\)? To produce \({\rm{12}}\;{\rm{V}}\)? Why is \({\rm{24}}\;{\rm{V}}\) better than \({\rm{12}}\;{\rm{V}}\) for starting the truck’s engine (a very heavy load)?

Short answer

A larger voltage gives more power. Thus, \({\rm{24\;V}}\) battery is used in the starter system.

Step-by-step solution

Relation between power and voltage

Power and voltage are proportional to each other if the current is kept constant

Step 2: Connection of batteries to get \({\rm{24V}}\)

For creating a voltage \({\rm{12\;V}}\), connect two batteries in parallel, whereas connect two in series to generate a voltage \({\rm{24\;V}}\). It is better to put \({\rm{24\;V}}\)for starting a heavy load because a lower voltage will not be able to produce the required power as the applied resistance will be higher.