What is the main purpose of a resistor in an electrical circuit?

The main purpose of a resistor in an electrical circuit is to limit the flow of electric current. Resistors are designed to provide a specific amount of resistance against the flow of electrons, which effectively reduces the current that can pass through a circuit. This characteristic is crucial for controlling and managing current levels to prevent damage to other components within the circuit, ensuring safe and functional operation.

For instance, in a simple circuit with a power source and a light bulb, adding a resistor can prevent excessive current from flowing to the light bulb, which could potentially burn it out. By limiting the current, resistors also help in dividing voltages across components in a series circuit according to Ohm's law—V = IR, where the voltage drop across each resistor is proportional to its resistance.

Understanding this function clarifies why the other options do not accurately describe the role of a resistor. Amplifying current directly contradicts its function, while inducing magnetic fields pertains to inductors and transformers, and increasing voltage relates to devices like transformers as well. Therefore, the limiting of electric current is fundamental to the function and purpose of resistors in various applications.