How Tesla's induction motor created a rotating magnetic field

Historian David Bell argues that Napoleonic-era wars became a society-wide experience, not just contests between monarchs. Universal conscription meant civilians became soldiers or provided essential support to armies at home. Bell argues that this helped foster the belief that military service was morally superior during a national crisis.

Morse radio signals use about 100–150 Hz of bandwidth, far less than the roughly 2,400–2,800 Hz used for single-sideband speech. Receiver filters can isolate the narrow signal, and the ear's natural selectivity helps distinguish it from interference, even when signals are weak.