Question

A starter motor of the car draws a current i=300A from the battery of voltage 12V. If the car starts only after 12min, what is the energy drawn from the battery.

Answer 1

we know that

Energy = Power x time

or

E = P x t

here,

t = 12min = 12 x 60 = 720 s

P = VI

where

V = 12 volts

I = 300 amps

so,

P = 12 x 300

thus,

P = 3600 W

now,

the energy drawn from the battery will be

E = 3600 x 720

thus, we get

E = 2.592 x 10⁶ J ~ 2.6 MJ