Assertion: magnetic field's energy | /r/Causes | arc
Facets:
value: across the switch contacts
type: LOCATION
Source sentences:
text: This doesn't occur when the magnet is switched on, because the limited supply voltage causes the current through the magnet and the field energy to increase slowly, but when it is switched off, the energy in the magnetic field is suddenly returned to the circuit, causing a large voltage spike and an arc across the switch contacts, which can damage them.