Final answer:
To create 24 V for a semitractor truck's starter, connect two pairs of 12-V batteries in series and then connect those pairs in parallel. For 12 V, connect all four batteries in parallel. A 24 V system is preferred for starting heavy engines as it provides more power and allows for lighter wiring. option a is the correct answer.
Step-by-step explanation:
Semitractor trucks commonly use a set of four large 12-V batteries to power various electrical components. For starting the truck's engine, which is a heavy load, the starter system requires 24 V, while the normal operation of other electrical components uses 12 V. The correct way to produce 24 V is option (a): Connect two pairs of batteries in series to produce 24 V per pair, and then connect the pairs in parallel to maintain the voltage while increasing capacity. To produce 12 V, all four batteries should be connected in parallel, which maintains the original voltage but increases the available current.
The reason why 24 V is more effective than 12 V for starting the engine is that higher voltage systems can provide more power. Connecting batteries in series increases the voltage, allowing for the higher power needed to start a large engine. A 24 V system also enables the use of smaller and lighter wires while still carrying the same power, as power is the product of current and voltage and higher voltage allows for lower current to transmit the same amount of power.