Which statement is true about energy storage in an antenna?

Which statement is true about energy storage in an antenna?

• A. The energy stored is associated with the Induction field
• B. The energy stored is associated with the Radiation field
• C. Energy is stored equally in both fields
• D. Energy is stored in neither field

Answer: (A)

When an antenna is driven by a sinusoidal source, part of the input power is radiated away as electromagnetic waves and part is stored temporarily in the near field as reactive energy. This stored energy is tied to the magnetic portion of the near field, often described as the induction field, because it arises from the changing current and the resulting magnetic energy around the conductors. The radiation field, by contrast, carries energy away from the antenna; it’s energy in transit, not stored. So, the statement that energy storage is associated with the induction field best captures the idea of reactive energy in the near field, even though there is also electric energy stored in the near field and energy in the near field continuously oscillates between electric and magnetic forms.

When an antenna is driven by a sinusoidal source, part of the input power is radiated away as electromagnetic waves and part is stored temporarily in the near field as reactive energy. This stored energy is tied to the magnetic portion of the near field, often described as the induction field, because it arises from the changing current and the resulting magnetic energy around the conductors. The radiation field, by contrast, carries energy away from the antenna; it’s energy in transit, not stored. So, the statement that energy storage is associated with the induction field best captures the idea of reactive energy in the near field, even though there is also electric energy stored in the near field and energy in the near field continuously oscillates between electric and magnetic forms.