Power supply in parallel connection test
With a real 10A supply you have no guarantee at what exact current the supply will cut off. Some supplies may be designed to supply brief surges well in excess of the maximum continuous current. 

If this is a homework problem, consider that real wires are not zero resistance and even cheap voltmeters can detect typically +/-50uV DC on the 200mV (+/-199.9mV)scale. AWG 16 wire has a resistance of about 4m\$\Omega\$ per foot. 

Calculate what the minimum length of a sensible gauge of wire would be required to present a detectable voltage drop at the operating current using Ohm's law.