In a series circuit, what is true about current through the components?

• A. The same current flows through each component.
• B. The current doubles as it passes the first component.
• C. The current is proportional to the last component's resistance.
• D. The current depends on the parallel branches.

Answer: (A)

Current in a series circuit remains the same through every component because charges have only one path to travel. The same amount of current that leaves the source must pass through each element in turn, so I is constant along the loop. The voltage is shared among components according to their resistances: V_i = I R_i, and the total voltage is V = I(R1 + R2 + ...). The total resistance is the sum of the individual resistances, which sets the current via I = V / R_total. The other statements aren’t true for a series circuit: there aren’t parallel branches to split current, and there isn’t a mechanism for the current to double or to depend on just the last component’s resistance.