It depends on the device in question. Most of the time a properly crimped terminal is appropriate.

The device in question was either a SP switch or a 15A or 20A duplex receptacle.

Thanks

Crimp is not required by code.

As long as the device doesn't state solid only on it (or it's instructions) direct to the screw is fine. Make sure that you "squeeze out" any of the strands while tightening the screw.

Twist the stands together tightly, then place under the screw.

No spade lug is required.

jaysgarden - if you haven't noticed by now, lots of experienced, skilled tradesmen have particular ways that they want things done. Most times, those particulars exceed code. Nothing forces them to do that except for pride in their work and a sincere belief that a particular practice leads to superior results.

If you are lucky enough to have a teacher that falls into that category, I wouldn't go busting his chops quoting minimum code. Instead, I'd ask him why he thinks crimping works better. "Why" he recommends it will teach you more than "that" he recommends it.

Bill I've noticed that. This teacher is not my teacher but a family member in high school. I have no problem with his suggestion. When I strip stranded wire for attachment to a screw terminal on an switch or receptacle, I leave the piece of insulation on the ends of the wire to kind of hold the ends together.

It also helps to twist the strands counterclockwise. They tend to untwist less as you tighten the screw.

Another trick is to tin just the very end of the wire, about the last 1/8" or so, to hold the strands together. However, it's time consuming and I don't usually have that much patience.

Crimping on a spade lug is relatively quick and easy.

Another trick that helps a bit with stranded wire -- avoid using it. :-)

Strip the wire as you normally would. Twist the strands. The strip another 1/16" of insulation. Slide the little piece of insulation to the end of the wire. That helps keeps the strands in place as you wrap them around the screw.

I didn't know stranded wire existed for running in walls etc.

Not common for the gauges usually connected to switches but it's possible. One common case is that some devices (dimmers, timers) may have their own stranded leads connected that you may want to put under a screw on an adjacent device or terminal.

"I didn't know stranded wire existed for running in walls etc."

Stranded is preferred for pulling into conduit systems.

Using back-wired (not backstab!!) devices makes using stranded wire a lot easier.

I used miles of stranded romex when I worked as the lead in the electrical area for a company years ago that got into the cabin cruiser business. It was interesting to work with. It was like an extension cord with a romex jacket.

I'd love to get my hands on a few thousand feet of that!