EMP sends out a wave of electromagnetic energy (four waves, actually) and this wave induces electric current in wires.
Pass a wire through a magnetic field and current is induced. This is how a generator works. But with EMP, the wire is fixed and the magnetic wave is moving. Imagine how much current would be induced in a 100-mile long power line. Now, how much current would be induced in the half-inch wire between the battery and the processor in your quartz watch? Nobody can say for certain.
CME - Corona Mass Ejections are the nearest thing to EMPs that we have experienced. That being said there was a CME in 1857 that could be said to be the “model” of a hostile EMP attack. It was powerful enough to induce telegraph line to ground sparking, temporarily knock out telegraph communication and electrocute some telegraph operators (As near as I can tell from the accounts I have read none were killed!).