by and with in passive voice

[atabitaraf]

At the end of passive sentences we can mention the subject using 'by' and sometimes 'with' is used at the end of passive sentences.
The apple was eaten by John.
The apple was eaten with knife.
I heard somewhere that if you want to refer to a human, animal, or an electrical or diesel machine you can use 'by' and for the other things you have to use 'with', am I right?

 

[5jj]

I heard somewhere that if you want to refer to a human, animal, or an electrical or diesel machine you can use 'by' and for the other things you have to use 'with', am I right?

No. We use 'by' for the agent, and 'with' with the tool.

 

[Raymott]

The apple was eaten with a knife.
The paper was cut by a knife. = The knife cut the paper. (The knife is the agent).
The paper was cut with a knife. = Someone cut the paper with a knife. (Someone is the agent).
John cut the paper with a knife.

 

[tzfujimino]

Hello.:-D
I'm not sure if it's a relevant question to ask here, but...

"The top of Mt. Fuji is covered with snow."

Is it possible to use 'by' instead of 'with' in the sentence above?

Thank you.

 

[Raymott]

Hello.:-D
I'm not sure if it's a relevant question to ask here, but...

"The top of Mt. Fuji is covered with snow."

Is it possible to use 'by' instead of 'with' in the sentence above?

Thank you.

Yes, you can use 'by'. If you can imagine the snow being the active agent that did the covering, you can use 'by'.
I would say "covered in snow", but that's just another option.
In fact, 'with' tends to mean that someone covered it with snow; but it's not wrong.