A car battery with 12 V and negligible internal resistance (r=0) is connected three identicle resistors with R=20.
a. find the current and power of each resistor consumes when the switch is open.
b. find the current and power of each resistor consumes when the switch is closed.
c. if the battery becomes old and the internal resistance of the battery is r=1.00, with the switch closed, find the voltage applied on ther resitor on the left and the power dissipated on the battery due to the internal resistnace.