In a series circuit with resistors 3 Ω and 7 Ω, the total resistance is:

• A. 4 Ω
• B. 10 Ω
• C. 21 Ω
• D. 7 Ω

Answer: (B)

In a series circuit, resistors simply add because the same current flows through each one, so the total resistance is the sum of the individual resistances. R_total = R1 + R2.

Here, R_total = 3 Ω + 7 Ω = 10 Ω. So the value 10 Ω is the total resistance.

The other numbers don’t fit because they don’t come from adding the two resistors in a single path: 7 Ω would ignore the 3 Ω, 4 Ω would require a different combination, and 21 Ω would come from multiplying or a different setup.