Which of the following correctly lists three purposes for including a resistor in a circuit?

• A. Limit current, set bias, divide voltage
• B. Store energy, shield voltage, cool components
• C. Increase current, decrease resistance, amplify signal
• D. Provide a source of energy, power the load, create magnetism

Answer: (A)

A resistor is used to control current, set bias points for active devices, and create voltage divisions in a circuit. According to Ohm’s law, the current through a resistor is I = V/R. For a fixed supply, higher resistance lowers current, while lower resistance raises it. This makes resistors ideal for limiting current to protect components like LEDs or transistors, and for establishing a stable operating point by providing a known voltage level to bias a transistor or other active device. When resistors are placed in series, the voltage across each resistor is proportional to its resistance, allowing the total voltage to be divided to generate reference voltages or bias points.

Other roles listed aren’t typical resistor functions: resistors don’t store energy (that’s capacitors or inductors), they don’t shield voltage, and they don’t cool components. They aren’t sources of energy and don’t amplify signals; they simply resist current and shape how that current and voltage are distributed in the circuit.