P28_019.PDF

19. The potential diﬀerence across each resistor is V =25 . 0V. Since the resistors are identical, the current

in each one is i = V/R =(25 . 0V) / (18 . 0Ω)=1 . 39A. The total current through the battery is then

i total =4(1 . 39A) = 5 . 56A. One might alternatively use the idea of equivalent resistance; for four

identical resistors in parallel the equivalent resistance is given by

R eq = 1

R = 4

R .

When a potential diﬀerence of 25 . 0V is applied to the equivalent resistor, the current through it is

the same as the total current through the four resistors in parallel. Thus i total = V/R eq =4 V/R =

4(25 . 0V) / (18 . 0Ω)=5 . 56A.