Answer: External resistance = internal resistance.
- A Internal resistance = 0
- B External resistance = internal resistance
- C External resistance >> internal resistance
- D External resistance << internal resistance
Correct answer: B. External resistance = internal resistance
Explanation: Maximum power transfer: P = E<sup>2</sup>/(4r) when R<sub>external</sub> = r<sub>internal</sub>. This is the maximum power transfer theorem.
In series, the same current flows through both resistors; in parallel, the current splits between branches and the voltage across each resistor is the same.
Concept context
Ohm's law, resistors, Kirchhoff's laws, Wheatstone bridge, and cells.