Motor power


i want to do this with a motor but if i use 10k resistor the motor don’t rotate, if i use 68omh the motor rotate
now i have only 10k and 68ohm resistor
why we use always 10k resistor? is to protect arduino?
the arduino current for i/o pin is 40mA…5v/40mA=125ohm can i use 125ohm resistor or i risk to damage arduino?
Excuse me for my engish but i speak english a little

Post the datasheet for the transistor.

(Also, your Fritzing should show the 9V battery power going into the ext dc pwer barrel jack.)

i have found the image on internet
this is the datasheethttp://www.fairchildsemi.com/ds/SS/SS8050.pdf

http://www.fairchildsemi.com/ds/SS/SS8050.pdf

Did you read the datasheet before trying to use it ?
IT IS AN NPN TRANSISTOR , NOT PNP LIKE SHOWN IN THE FRITZING SO THE WIRING SHOWN WITH THE WRONG TRANSISTOR AND THE WRONG ORIENTATION IS MEANINGLESS.

Correct the drawing to reflect the part you are using and the fact that it is NPN and NOT PNP and repost the diagram.
I don’t know why you don’t just draw the schematic on a piece of paper and take a photo. How hard can that be ?

SS8050.pdf (158 KB)

The fritzing diagram shows only one wire going between the bottom half and the top
half, so by definition it cannot be a circuit. Electricity flows round a circuit, so there
needs to be at least two wires joining any part of the circuit to any other part.

In particular here common ground (or is it common +5V) are needed for the
transistor to switch.

The fritzing diagram shows only one wire going between the bottom half and the top
half, so by definition it cannot be a circuit. Electricity flows round a circuit, so there
needs to be at least two wires joining any part of the circuit to any other part.

I can't believe I didn't spot that LOL ! XD

That's funny ..