Question

A closed loop consists of a \(15\ \text{V}\) battery, a \(5\ \text{V}\) battery (opposing the first), and a \(25\ \Omega\) resistor. The current through the loop is

• A. \(0.8\ \text{A}\)
• B. \(0.2\ \text{A}\)
• C. \(1.2\ \text{A}\)
• D. \(0.4\ \text{A}\)

Hint:

The batteries oppose each other, so the net emf is their difference. Divide it by the resistance.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
When two cells oppose each other in a loop, the net emf is the difference of the two, and the current flows in the direction set by the larger cell.

Step 2: Net emf
\(E_{net}=15-5=10\ \text{V}\)

Step 3: Calculation
With only the \(25\ \Omega\) resistor limiting the current, \(I=\dfrac{10}{25}=0.4\ \text{A}\).

Final Answer:
The current in the loop is 0.4 A. \[ \boxed{\text{(D) }0.4\ \text{A}} \]