When a 100-Ω resistor is connected to a battery of emf E and internal resistance r, the battery delivers a power P = 0.794 W. When a 200 Ω resistance is connected to same battery it delivers a power P = 0.401 W. What are the emf and internal resistance of the battery?
A)E = 10 V, r = 5 Ω
B)E = 4.5 V, r = 4 Ω
C)E = 18 V, r = 4 Ω
D)E = 9 V, r = 2 Ω
E)E = 12 V, r = 6 Ω

Question

Quizplus · Accepted Answer

Using the power formula P = V^2/R and the fact that V = E - Ir, we can set up equations for both scenarios and solve for E and r. Solving these equations gives E = 9 V and r = 2 Ω.

When a 100-Ω Resistor Is Connected to a Battery of Emf