Which of these represents components that generate a voltage?

[Jerry]

Which of these represents components that generate a voltage?

I'm pretty sure its A only. Do you agree?
Thanks for the help.

[Jerry]

Instead of just answering which one is correct, let’s talk about what each of them mean.

1. Symbol A is typically seen without the circle around it.  The circle just tends to throw you off.  This is the symbol for a DC power source, and that does make this the correct answer.
2. Symbol B is not a commonly used symbol however some people may attempt to use this symbol to represent a thermister(a resistor that changes value depending on it’s temperature).
3. Symbol C is a photodiode(a diode that can be activated by light).  This symbol also is often seen without the circle around it.
4. Symbol D.  I have never seen this symbol before, therefore I would conclude that it is not a circuit symbol.
5. Symbol E is a phototransistor(a transistor that can be activated by light)
6. Symbol F almost looks like a thermistor symbol but it has an extra line in it, so it is not the thermistor symbol.  I don’t recognize this as an electronic circuit symbol.
7. Symbol G is a gated diode but it has the arrows showing light shining on it.  It seems that they have combined two different symbols into one which means this is not a valid symbol, but that could change with technology changes.