From: jasen@xnet.co.nz   
      
   On 2017-12-15, mrdarrett@gmail.com  wrote:   
   > Hi everyone,   
   >   
   > When regulating the power to a motor or light, does the triac do so   
   > efficiently or does it dump the unwanted power as heat, as a linear   
   > voltage regulator does?   
      
   It does it by switching on and off really fast, most of the unwanted   
   energy is blocked. (and not consumed, it "stays in the power line")   
      
   There's a 1.5 volt ineficiency (ballpark figure) added by the triac, so   
   if you're running a 10A load at full power the triac will get about   
   15W of heat.   
      
   Triacs are used in variable speed hand-tools (mains powered)   
   and incandescent lamp dimmers (amongst other uses) feel free to probe   
   the outside of these devices with a heat-sensitive finger :)   
      
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