A 9 V source powers three 2 Ω resistors in series. What is the current?

• A. 0.75 A
• B. 2 A
• C. 1.5 A
• D. 3 A

Answer: (C)

In a series circuit, resistors add up to give the total resistance, and the same current flows through each component. Three 2 Ω resistors in series give a total resistance of 2 + 2 + 2 = 6 Ω. Using Ohm’s law, the current from a 9 V source is I = V / R = 9 V / 6 Ω = 1.5 A. So the current is 1.5 amperes.

If you check the other possible currents: 0.75 A would require a total resistance of 12 Ω, 2 A would require 4.5 Ω, and 3 A would require 3 Ω, none of which match the 6 Ω total in this setup.