A 100Ω resistor and a 200Ω resistor are connected in series to a battery. How does the current through the 100Ω resistor compare to the current through the 200Ω resistor?
AThe current through the 100Ω resistor is twice as large, since it has less resistance
BThe current through the 200Ω resistor is twice as large, since it draws more power
CThe current is the same through both resistors
DThe current splits evenly between the two resistors
In a series circuit, the same current flows through every element — this is a direct consequence of charge conservation. Charge cannot accumulate inside a conductor at steady state, so every coulomb of charge that enters any cross-section must exit. The resistors have different resistances (and the voltage drops across them will differ), but the current — the rate of charge flow — is identical at every point in the series path. The common misconception is that more resistance 'uses up' more current; what changes is voltage, not current.
Question 2 Multiple Choice
In a circuit diagram, the arrow representing conventional current in a wire points to the right. Which way are electrons actually moving?
ATo the right — conventional current and electron flow are in the same direction
BTo the left — conventional current is defined as positive charge flow, opposite to electron movement
CIn both directions simultaneously, since electrons oscillate
DThe diagram cannot tell us — conventional current says nothing about electron motion
Conventional current is defined as the direction positive charges would flow — from higher to lower potential. Electrons carry negative charge and flow from low to high potential, which is opposite to conventional current. So if conventional current arrows point right, electrons are moving left. This historical convention (established before the electron was discovered) is universally used in circuit analysis, and it produces correct results as long as applied consistently. The mathematics is identical regardless of which convention you use.
Question 3 True / False
In a series circuit, the same current flows through every component because charge is conserved and cannot accumulate inside the conductor.
TTrue
FFalse
Answer: True
This is the physical basis of Kirchhoff's Current Law. Charge cannot be created or destroyed, and at steady state, charge cannot build up at any interior point — the resulting electric field would immediately redistribute it. Therefore, the rate of charge flow (current) into any segment must equal the rate out. In a single-path (series) circuit, this means the current is identical everywhere in the loop.
Question 4 True / False
When current passes through a resistor, some of the current is consumed — less current exits the resistor than enters it.
TTrue
FFalse
Answer: False
This is one of the most common misconceptions in basic circuit theory. Current is not 'used up.' The same charge that enters a resistor exits it — the number of electrons is conserved. What changes is the energy carried by those charges: voltage drops across the resistor as the charges transfer energy to it (as heat). Current is conserved; voltage is not. The distinction between current (charge flow rate) and energy (what gets dissipated) is fundamental to all circuit analysis.
Question 5 Short Answer
Why does charge conservation imply that the same current flows through all elements in a series circuit, even though those elements may have very different resistances?
Think about your answer, then reveal below.
Model answer: At steady state, charge cannot accumulate inside a conductor. If more charge per second were entering a wire segment than leaving, charge would pile up, creating an electric field that would oppose further buildup and push charge forward until flow balanced. This self-correcting mechanism enforces equal current everywhere in a single-path circuit. Resistance affects how much voltage is required to drive a given current through a component, but it does not change the fact that charge is conserved and the same current must pass through each element in series.
The conceptual key is that current continuity is not a coincidence or a rule to memorize — it is an inescapable consequence of charge conservation combined with the impossibility of steady-state charge accumulation. Kirchhoff's Current Law is just this physical principle stated as a circuit rule: what flows in must flow out at every node.