Final answer:
An inductor is the circuit element that opposes rates of change of current by producing an induced emf according to Lenz's law, which acts to oppose changes in current. It is not to be confused with resistors, which impose a voltage drop directly proportional to the current following Ohm's law.
Step-by-step explanation:
The type of circuit element that opposes rates of change of current is an inductor. An inductor works by producing an induced electromotive force (emf) that acts to oppose changes in the current flowing through it, according to Lenz's law. This property is a manifestation of Faraday's law of electromagnetic induction, which forms the foundation for how inductors function.
When the current in an inductor is altered, for instance when it's turned on or off, it induces an opposing voltage that acts against the change in current. This is why inductors are sometimes referred to as having 'inductive reactance', which is a form of AC resistance. The opposition to the change in current by an inductor continues until the current stabilizes to a constant value or the inductor's stored magnetic energy has been fully employed.
It's important to note that while resistors also impede current by producing a voltage drop proportional to the current passing through them, this is associated with direct current (DC) and is described by Ohm's law. On the other hand, inductors specifically oppose changes in current, particularly in alternating current (AC) circuits.
The unit of resistance is the ohm (Ω), which is defined as a volt per ampere of current. However, in the context of inductors, the relevant measurement is inductance, which is measured in henries (H).