What electrical component is used to oppose the flow of current in a DC circuit?

In a direct current (DC) circuit, a resistor is the component specifically designed to oppose the flow of current. When current flows through a resistor, it encounters resistance, which causes a drop in voltage across the resistor according to Ohm's law (V = I × R), where V is the voltage, I is the current, and R is the resistance. This property of resistors allows them to control the current in a circuit, protect sensitive components, and divide voltage.

The other components mentioned serve different functions. An inductor, for instance, opposes changes in current and is primarily used in alternating current (AC) applications. A voltmeter measures voltage, rather than opposing current flow, and is used for testing rather than controlling current. A transformer alters voltage levels between AC circuits and does not function in DC circuits as it requires a changing magnetic field to operate effectively. Thus, the resistor is the essential component that directly relates to opposing current flow in a DC circuit.