Question

A surging current in an antenna

A. Leads to the generation of static magnetic field

B. Leads to the emission of an electromagnetic wave

C. None of these

Answer 1

A surging current in an antenna leads to a temporary staic generation of magnetic field around it .

There are many ways to avoid equipment failure due to surge currents. Such a current can be internally or externally generated. An internally generated surge current is usually the result of the capacitor surge current, which results when a capacitor or condenser is previously uncharged followed by a sudden flow of current that is meant to equalize the capacitor voltage to the source circuit.

An externally generated surge current usually comes from lightning. Despite attempts to protect sensitive equipment from lightning surge, there is always a way that such currents can be induced into energized equipment. Energized equipment may have power feeders and miscellaneous cables, such as interface cables and signal cables that carry radio frequency, audio, or data.

In radio frequency systems, the antenna, usually on an antenna tower elevated above the ground, is always where signal level is best. The same ideal place for tapping the radio frequency signal is also where lightning surge is most likely to occur. Lightning rods are placed at the highest point of such towers to “catch” most of the lightning surge, but some of the surge energy finds its way into the electronic equipment.