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22 DESIGN007 MAGAZINE I JULY 2024 In circuit theory, we learn that current flows in a closed loop, returning to the source via a conductor pair. is flow of current provides power to the load, and energy transfer occurs as described by Ohm's law (P = VI). Conversely, in electromagnetics theory, we discover that current does not provide the power in a cir- cuit, but rather the energy wave is guided by the conductor to power the load, according to Maxwell's equations. e flow of current in a PCB is essential for delivering energy and enabling devices to per- form work but does current carry the energy? Why does an alternating current (AC) signal require a thicker conductor to provide higher power if the current is not in the carrier? ere Does Current Deliver the Energy in a Circuit? are many contradictions as to how energy flows in a circuit. To understand this, one must appreciate the difference between the lumped element view and that of distributed circuits. Ohm's law provides a simplified approach to power transfer whereas Maxwell's equations offer an interpretation of the entire distributed system. In this month's column, we will try to clarify the perplexing aspect of AC/DC electri- cal theory. Electromagnetic (EM) waves carry energy through their electric and magnetic fields. e larger the strength of these fields, the more work they can do and the greater the energy the wave carries. At high frequencies, the diameter of a conductor affects how efficiently it absorbs Beyond Design by Barry Olney and Rick Hartley (Special Advisor), IN-CIRCUIT DESIGN PTY LTD / AUSTRALIA