what are the ways that pressure generates electricty?

Answer 1

It's called the piezoelectric effect. Basically it uses a special crystal such as quartz. These crystals have a cool property. When the crystal is compressed or stretched, it develops an electric potential across it(positive or negative depends on whether it's being compressed/stretched). Conversely, if you apply an electric current across the crystal, it will compress or stretch(whether it stretches or compresses depends on the polarity of the voltage applied). In case of quartz, it operates at an extremely precise frequency, which is why it used in timekeeping devices.

Answer 2

The best-known mechanism is piezoelectricity, when a material responds to changes in pressure (or mechanical stress) by generating a voltage.

Answer 3

N put pressue on S, where N = north, S = south, magnetic poles!!