Ground wires let fuses blow

Electrical · System Grounding · printed page 91 (PDF page 92)

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Ground Wires let Fuses Blow Electric System – Grounding System Grounding – Electrical

Text in the illustration

distribution panel
STOVE
main bus bars
15 AMP FUSE
ground wire
( panel grounded through metal conduit from service entrance)
black (hot) wire shorting against panel box
household circuit
neutral wire
neutral bus bar
since the panel is grounded, the black wire shorting against the metal sides allows the electricity to flow easily to ground (very little resistance) - the resulting high current flow immediately blows the fuse (deactivating the circuit)
if the panel weren't grounded properly and someone touched the metal box, electricity would flow through the person (enough to kill them), but possibly not enough to blow the fuse

Generated explanation

The illustration shows a metal electrical distribution panel with main bus bars, six 15-amp plug fuses, a stove fuse block, and a neutral bus bar. A household branch circuit enters the panel at the right, where a circled detail shows its black hot wire shorting against the metal enclosure. A ground wire and grounding through the metal service-entrance conduit are identified. The annotations explain that grounding provides a low-resistance fault-current path so the resulting high current blows the fuse, disconnecting the circuit. They also warn that an improperly grounded enclosure could conduct lethal current through a person without enough current to blow the fuse.