15 amp switch/ receptacle on 20 amp line
 

Can a 15 amp light switch or 15 amp receptacle be put on a 20 amp circuit (wire)?

thanks

Yes, but it can't be the ONLY device on the circuit.

A 15 amp switch can be used on a 20 amp circuit as long as the load it is controlling is less than 15 amps.

15 amp receptacles can be used as long as there are more than one receptacle on the circuit. Bear in mind a duplex receptacle is TWO receptacles.
Example: You cannot put a single (simplex) 15 amp receptacle on a 20 amp circuit, but you can put a duplex.