Confusion about relay
Since a Relay>2A has special conductive high temp tungsten or other plating alloys , it is designed to withstand a certain amount of >10,000'K arc temperatures for so many times at so many milliseconds or microseconds depending on the load reactance and current.

You supply the voltage, not the relay. But the load also affects the switch off voltage and current or starting surge current to big caps.

Since AC normally quenches current at or near the Zero crossing , it has a higher rating, but DC motors for example act as generators when switched off and thu current is sustained like an SCR until quenched or until the current drops below the holding current when opened. 

For this reason , DC ratings are lower than AC ratings on all switched contacts.  

For those who wish to research this further , see all of OMRON's Application Notes on Relay Contacts

example 

another example