Valero Mechanical Aptitude Practice Test

In a series circuit, resistances add together to form the total resistance. When you place another resistor in series, you’re adding its resistance to what’s already there, so the overall resistance becomes larger. With a fixed voltage, this higher total resistance also means the current decreases, but the key point for the question is that the total resistance increases when another resistor is added in series. It wouldn’t stay the same or decrease, and doubling would only happen if the new resistor happened to equal the existing total, which isn’t required by the basic rule.