an EMP is an electron pulse. any exposed wire will pick it up. And any coil of wire will multiply the signal.
Because of the intense electromagnetic fields (about 10 kV/m to 50 kV/m ) and wide area of coverage, the HEMP can induce large voltages and currents in power lines, communication cables, radio towers, and other long conductors serving a facility. Some other notable collectors of EMP include railroad tracks, large antennas, pipes, cables, wires in buildings, and metal fencing. Although materials underground are partially shielded by the ground, they are still collectors, and these collectors deliver the EMP energy to some larger facility. This produces surges that can destroy the connected device, such as, power generators or long distance telephone systems.
Semiconductor devices fail when they encounter an EMP because of the local heating that occurs. When a semi-conductive device absorbs the EMP energy, it displaces the resulting heat that is produced relatively slowly when compared to the time scale of the EMP. Because the heat is not dissipated quickly, the semiconductor can quickly heat up to temperatures near the melting point of the material. Soon the device will short and fail. This type of failure is call thermal second-breakdown failure.