Two identical batteries, each with an emf of 18 V and an internal resistance of 1 $\Omega$, are wired in parallel by connecting their positive terminals together and connecting their negative terminals together.The combination is then wired across a 4-$\Omega$ resistor.The current in the 4-$\Omega$ resistor is:
A)2.0 A
B)3.6 A
C)4.0 A
D)7.2 A
E)9.0 A

Question

Quizplus · Accepted Answer

When two identical batteries are connected in parallel, the overall emf remains the same as a single battery (18 V), but the effective internal resistance is halved (0.5 ohms) because the resistances of the two batteries are in parallel. The total resistance in the circuit is the sum of the effective internal resistance and the external resistance, which is 0.5 ohms + 4 ohms = 4.5 ohms. Using Ohm's law (V = IR), the current through the 4-ohm resistor can be calculated as I = V/R = 18V / 4.5 ohms = 4.0 A.

Two Identical Batteries, Each with an Emf of 18 V Ω\OmegaΩ

Two Identical Batteries, Each with an Emf of 18 V $\Omega$