How does a resistor reduce current without using up charge?

A resistor can limit the current in a circuit while the same amount of charge per second enters and leaves it. It does not consume electrons. Instead, the resistor's material and shape determine how much voltage is required to sustain a particular current, while electrical energy is transferred mainly into thermal energy.

Inside a conductor, an electric field influences mobile charges. Their motion interacts with the material's microscopic structure, including vibrations and imperfections. Energy supplied by the circuit is transferred to that structure. The charges continue through the circuit, but energy becomes more spread out in the resistor and its surroundings. This separates two ideas that are easily confused: charge is conserved, while useful electrical energy can be converted to heat.

For an ordinary ohmic resistor held near a constant temperature, voltage V and current I are related by V = IR, where R is resistance. Across the same 6-volt supply, a 300-ohm resistor carries 0.02 ampere in the simplified circuit, while a 600-ohm resistor carries 0.01 ampere. Doubling resistance halves current when voltage is fixed. That comparison does not mean the current gradually shrinks as it passes through one resistor.

For a uniform piece of the same material, a longer path generally has more resistance and a wider cross-section less. Resistivity describes the material itself; resistance also includes the component's dimensions. Temperature can change resistivity, so the simple relationship has conditions. A filament lamp, for example, becomes much hotter as it brightens and does not behave like one fixed resistance over its full operating range.

The rate of energy transfer is electrical power, P = VI. A resistor must be designed to release that heat without exceeding its safe temperature. In a circuit containing an LED, the resistor helps establish a suitable operating current, while the LED's own voltage–current behavior also matters. The circuit must be considered as a whole. A resistor is a controlled route for charge and energy, not a tiny container that catches and destroys electrons.