my god, i have no sense of direction! (1 Viewer)

[1234567]

p type
n type
in this semiconductor material / solar cells
electron flow from p to n
and holes (current ) flow from n to p
right?

then why is it that when u connect it into a circuit, you 'd have to connect the p type to positive terminal and n type to negative terminal/ doesn't that mean in this case, the current goes from p to n? which opposes the current created in te semi conductor???
explain please.

 

[1234567]

damn i always lose direction

say if in a motor, the current goes left to right in the conductor in the magnetic filed, the back emf would go right to left.
and say we have a generator, that has exactly the same magnetic filed, would the generated electricity be in the direction of the back emf of th emotor, or the conventional current flow in the motor?

 

[BlackJack]

Think about it for a while...
Hole flow from n to p inside the semi-conductor... e- flow from p to n...

Therefore at the p end it's positively charge and at the n end it's negatively charged...
A potential difference...

Current goes from P to N along the outer circuit, and from N to P inside the cell... it completes a cycle of the entire circuitry.

solar cell:
P |--->-->--- to circuit
^-|
N |---<---<-- from ciruit

 

[BlackJack]

back emf of the motor.

edit: hmmm... looks like they stopped updating the main page & sections to keep the server running... only the threads are active...

 

[1234567]

so .. for the second part
when we are determining the direction of the produced electricity in a generator, we need to use the force opposite to the rotational torque and then use the handrul to determine the direction?

 

[BlackJack]

How so? We're still using the same rotational torque...

 

[1234567]

arrrrrrrrr
i am confusssssssseeeeeeeeedddddddddd


coz u know in a motor, the back emf is in the oppsite direction of the current.................
so......
when u determine the generator, do u just determine the direction of the current (that would be flowing through if it is a motor), and then reverse that direction , and say taht the reversed direction is the induced electricity?

 

[superhubert]

yeah...it just followes the oppostite of the right hand rule..... the batabase....hmmmmmm. seems like i'm encountering a large resistance, there must be a large current flowing through the database!

 

[BlackJack]

Yes. That is coorect.

(next bit's just for understanding)
Okay. consider this. In the clockwise spinning motor, the force is caused by the input current. In the clockwise spinning generator, the force is generated by you hand rotating it. These are in the same direction. THey generate induced current in the same direction.

If that's confusing, then consider this:
Just look at the coil as a moving conductor in a magnetic field and work it out from there (no need to reverse current here.) This works either way (back emf in motor and current in generator).