Question 6A460

Antennas convert electrical energy into electromagnetic waves, radiating power into space. The radiated power can be calculated using a form of Ohm's Law for power. Option B, P = I² x radiated resistance, correctly describes this relationship. "Radiated resistance" is a theoretical equivalent resistance that represents the power an antenna radiates as electromagnetic waves. It's not a physical resistor, but a concept used to quantify how efficiently an antenna transfers electrical power from its input current (I) into the propagating electromagnetic field. Just like power dissipated in a resistor is I²R, the power *radiated* by an antenna is the square of the antenna current multiplied by its radiated resistance. Option A, P = I² x R, is too general. "R" could refer to various resistances (ohmic, input impedance), but for *radiated* power, it must specifically be the radiated resistance. Option C is incorrect as a direct relationship exists. Option D, P = E x I, is a valid power formula, but P = I² x radiated resistance is more specifically applicable to calculating the *radiated* power from an antenna's current.