Final answer:
Resonant circuits, which include a resistor, inductor, and capacitor, oscillate with maximum amplitude at a particular resonant frequency, enabling applications in filtering, tuning, and detection, such as in merchandise surveillance and metal detectors.
Step-by-step explanation:
Resonant Circuits in Electronic Surveillance
Resonant circuits are fundamental components in various electronic devices, including those used for the electronic surveillance of merchandise. A resonant circuit may consist of a combination of a resistor, an inductor, and a capacitor (RLC circuit).
This RLC circuit has a particular resonant frequency at which it can oscillate with maximum amplitude. When a circuit resonates at this frequency, it can either pass or block signals at this specific frequency, which is pivotal in applications such as radios, cell phones, and security tags.
Hertz's experiments in the late 19th century demonstrated the use of resonant circuits to generate and detect electromagnetic waves.
These circuits are still in use today for filtering and tuning purposes. In the context of merchandise surveillance, resonant circuits can be applied in security tags that respond to a specific frequency, allowing for detection when merchandise passes through an electromagnetic field tuned to that frequency.
Likewise, these principles are also utilized in metal detectors, where a change in self-inductance due to proximity to metal shifts the circuit's resonance, triggering a detection signal.