What does these electric components represent?

1)
Opamp (operational amplifier)
2)
could be a Voltage Source (usually there is a symbol in the circle)
3)
Constant Current Source

 

Why did you post this under "mathematics"? I would think it would do better under "Physics".

 

the first one looks like a comparator, not an opamp.

 

opamps can be comparators...

 

its been a while since i went thru opamps. but as far as i remember, opamps are made up of comparators.

 

Comparators as well as inverting amps, non-inverting amps, summers, differentiators, and integrators, etc are made up of op-amps. A comparator is an application of an op-amp.