When item of jewellery made of metals such as copper r nicker are placed in a solution having a salt of gold, a thin film of gold is deposited by:

When item of jewellery made of metals such as copper r nicker are placed in a solution having a salt of gold, a thin film of gold is deposited by:

Just keeping it for10 minutes

passing an electric current

Heating above 100 degree C

Cooling to below 0 degree C