Batteries in opposition reduce net voltage

Steps:

• Identify battery polarities: assume 12V and 8V batteries oppose each other in series.
• Calculate net voltage: 12V - 8V = 4V.
• Determine total resistance: assume 2Ω resistor in circuit.
• Apply Ohm's Law: I = V/R = 4V / 2Ω = 2A.

Why A is correct:

• Net emf of 4V across 2Ω yields I = 2A by Ohm's Law (V = IR).

Why the others are wrong:

• B ignores opposition, adding voltages for 20V and 10A, but not 4A.
• C assumes parallel batteries or misreads resistance, overestimating current.
• D adds voltages without resistance details, yielding unrealistically high value.

Final answer: A