When i insert sd card to my RPi2 model B, ACT led doesnt blink but it blinks for another rpi using same SD card.SD card & ethernet is fine.
Is there any problem with my RPi? If so, how can i determine it?
You won't necessarily notice the ACT light blinking; on a successful boot, once the kernel loads the ACT light only indicates SD card activity, whereas with a boot which fails before the kernel loads it will produce a regular pattern of blinks, possibly repeated in a loop, or (on the 2/+ models) if there is no SD card (or the reader does not like the card), a solid green ACT1.
Note on the A/B models, no SD card will not light ACT, which could be confused with a successful boot.
However, since there is generally more SD card action than just loading the kernel at boot, usually there will be irregular flickering for few seconds. Not noticing any, i.e., just getting a steady PWR, does not necessarily mean the boot failed, but it could, as a result of a kernel/init hang or hardware damage -- you would have to plug in a screen to tell the difference between these three things (successful boot, broken hardware, kernel or init hang).
Put another way, no ACT light could indicate:
1. This includes formatted cards that weren't intended for use in the pi.