Yes, definitely. This is very important, not only so that cars behind you know that you are switching lanes, but also the cars in the neighboring lane will know you are switching lanes.
As of 2010 the answer is no. It is recommended to use your turn signals when changing lanes, but not a law.
The PA Motor Vehicle Code, § 3334. Turning movements and required signals- says that you will use your turn signals or hand signals when you are turning or changing lanes.
Provided you don't need to use them (i.e. change lanes, pull over or turn a corner), yes.
When you are making a turn, when you are changing lanes, or when you are pulling away from the curb or are parallel parking. Activate turn signals 200' before making a turn.
Use your turn signal.
Whenever you are turning or changing lanes.
Turn signals do not have or use a solenoid.
You use your arms out he widow as signals.
Yes it is
Use hand signals.
No, turn signals are required on the vehicle.
Using common sense any time you change lanes even if all the traffic is traveling with you need to use your signals. Regardless of right of way you must always signal you intentions.