Problem 18CQ
Semitractor trucks use four large 12-V batteries. The starter system requires 24 V, while normal operation of the truck’s other electrical components utilizes 12 V. How could the four batteries be connected to produce 24 V? To produce 12 V? Why is 24 V better than 12 V for starting the truck’s engine (a very heavy load)?
Solution 18CQ
If battery are connected in series, the equivalent emf is equals the sum of emf of all the batteries. Therefore, two batteries of 12V rating should be connected in series, So that the demand of 24V could be met for the starter.
Also for the other electrical component of the trucks, two batteries of 12V rating should be connected in parallel to meet the requirement of 12V.
The loss of energy due to heat is proportional to the product of square of the current and the resistance. Keeping the other thing constant, the losses in 24V is half than 12V battery. This is the reason why 24V battery is preferred in case of heavily loaded truck.
