Current rating is dependent on the mass of the contact being able to absorb heat without excessive temperature rise. If you have disassembled a few switches you will understand that they are adequate to the task. And my 20 amp switches were rated for 277 volts, often found in newer buildings. More efficient but it gives really nasty shocks.

 

Current rating is dependent on the mass of the contact being able to absorb heat without excessive temperature rise. If you have disassembled a few switches you will understand that they are adequate to the task. And my 20 amp switches were rated for 277 volts, often found in newer buildings. More efficient but it gives really nasty shocks.

Generally yes, this is true. But for switching (for example) 5 volts at 20mA, using a 20 amp rated contact switch isn't advisable. Reason is that the large contacts can dissipate so much more than is being asked of them there's hardly any arc that can burn away carbon from the surface of the switch. You won't burn out the switch but it will fairly quickly become unreliable. While the size of the switch matters, exceeding the amperage rating of the switch isn't just about the heat on the contacts it's also about the mechanical properties of the materials used in the switch. You wouldn't use an 18 gauge wire to conduct 20 amps, the wire would get hot and possibly melt the insulation off or melt other soft materials around it. That's a large part of why you wouldn't use a tiny switch to manipulate the current of a large piece of machinery.

 

And my 20 amp switches were rated for 277 volts, often found in newer buildings. More efficient but it gives really nasty shocks.

I am not talking about your switches, I am talking about the (unknown) ones in the lamp the OP wants to use. I can guarantee you it does not use 20 Amp rated switches.