An 18 V battery with internal resistance is connected to the external circuit shown below
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Electric Circuits · Electric Circuits
Problem
An 18 V battery with internal resistance r=1.0Ω is connected to the external circuit shown below, where all connecting wires have negligible resistance.
• Resistors R1=3.0Ω and R2=6.0Ω are in series, forming branch X.
• Resistor R3=4.0Ω forms branch Y.
• Branches X and Y are connected in parallel across the battery terminals.
(1) Determine the equivalent resistance of the external circuit (everything outside the battery) as seen by the battery.
(2) Calculate the total current that leaves the positive terminal of the battery.
(3) Find the current in each branch and the current through each individual resistor.
(4) Compute the power dissipated in each resistor and the power lost as heat in the battery’s internal resistance.
(5) Using your results from part (d), evaluate the percentage of the chemical energy converted inside the battery that is actually delivered to the external circuit. Comment on how internal resistance affects the efficiency of power transfer.