Question

why do we turn on the headlight when measuring the battery voltage during a starting system test?

Answer 1

Dear Student,

Every body is non ideal. That is even though battery voltage is for example 15 volts, it won't be exactly 15 volts due to the series resistance present in the battery which is of very low value due to which there would be a voltage drop. Hence in order to measure that resistance or the voltage drop created by that resistor we need some current. When we turn ON the head light, current flows and voltage drop can be measured accordingly the resistance value can be known.

Thank You. Have a Nice Day.