In a DC series circuit the _______.

• A. Current is constant and voltage varies.
• B. Voltage is constant and current varies.
• C. Resistance changes with time.
• D. Power is zero.

Answer: (A)

In a DC series circuit, there is only one path for current, so the same current flows through every component. Because the current is the same throughout, the voltage across each element depends on its resistance (V = I × R). The total supply voltage is the sum of these drops, so the voltage is divided among the components and can vary from one element to another. This means the current is constant while the voltages across components differ. The other statements don’t fit: the current isn’t varying in a simple series circuit, resistances don’t have to change with time, and power isn’t zero as long as there’s current.