Net EMF in series circuit with opposing cells

Steps:

• Identify cell polarities from typical circuit diagram: 3V and 2V aid each other, 4V opposes.
• Calculate net EMF: 3 V + 2 V - 4 V = 1 V.
• Total resistance is 5 Ω (negligible internal resistance).
• Apply Ohm's law: I = net EMF / R = 1 V / 5 Ω = 0.2 A.

Why A is correct:

• Net EMF of 1 V divided by 5 Ω resistance gives I = 0.2 A per Ohm's law.

Why the others are wrong:

• B: Assumes net EMF of 4 V (e.g., 4 V alone), ignoring other cells.
• C: Assumes net EMF of 5 V (e.g., 3 V + 2 V), excluding 4 V opposition.
• D: Assumes all EMFs add (3 V + 2 V + 4 V = 9 V), ignoring opposition.

Final answer: A