Voltage is stepped up or stepped down by use of transformers. Also current is increased or reduced by transformers. This makes it easy for people in houses to receive voltage from transmission lines. welders can weld properly by increased current.

Hot metal surfaces emitte electrons, a condition known as thermionics emission.

Demonstration of Lenz's law of electromagnetic induction: emf induced produces a magnetic field that opposes the field that creates it.

How a rule is used to measure length with precision