copper

aluminium

iron

galvanized steel

500 ohms

1000 ohms

1500 ohms

2000 ohms

for the safety of the equipment

for the safety of the operating personnel

for the safety of the equipment and for the safety of the operating personnel

none of the above

grounding resistance should be as low as possible

grounding resistance should be as high as possible

grounding resistance should be always zero

none of the above

to provide low impedance

to discharge the charging capacitance to ground

protection for operating personnel

both 1) to discharge the charging capacitance to ground and 2) protection for operating personnel