Explanation: When an antenna is physically too short for a desired operating frequency, it exhibits capacitive reactance. To make the antenna resonant and appear "electrically longer," you need to cancel this capacitive reactance. An inductor, or coil, introduces inductive reactance. By adding a coil in series with a physically short antenna, its inductive reactance can be chosen to cancel out the antenna's capacitive reactance. This causes the antenna to resonate at the desired frequency, effectively making it behave like a physically longer antenna without actually increasing its physical size. This technique is known as "loading." A resistor adds resistance and dissipates energy, but does not change the antenna's electrical length or reactance. A battery supplies DC voltage and current, which is unrelated to RF antenna tuning. Conduit is a physical pipe for wires and has no direct electrical effect on antenna length.