WIRELESS device is not working with ubuntu

Had you had installed the restricted driver for your broadcom device? System->Administration->Hardware Driver.

from where can i get these drivers for free?

Go to System, then Administration, then Hardware. it should search for the drivers you need.For Free :)

Sorry, "Hardware" should be "Hardware Drivers".

Then if you are still in trouble with your wireless...

Please first connect your network card to the wireless router using an ethernet cable (also known as a LAN cable).

In order to gather essential troubleshooting information about your wireless card, please follow this procedure:

Step 1: Open Terminal from "Applications->Accessories->Terminal"

Step 2: Please copy-paste the following command from this page in browser Firefox into the Linux Terminal.
Do NOT copy-paste from the Email message into the Terminal, as that will only copy PART of the command.
The command STARTS with the word sudo and ENDS with the word dist-upgrade;
So please copy-paste the ENTIRE command below from Firefox into a Terminal, press <enter>,
then enter password when sudo asks for password, then press enter again.

sudo dpkg --configure -a; sudo apt-get -f install; sudo apt-get update; sudo apt-get dist-upgrade;

Then reboot your pc and test if your wireless card is detected, if not continue from the step 3 below

Step 3: Please copy-paste the following command from this page in Firefox into the Linux Terminal.
Do NOT copy-paste from the Email message into the Terminal, as that will only copy PART of the command.
The command STARTS with the word sudo and ENDS with the word restart.
So please copy-paste the ENTIRE command below from Firefox into a Terminal, press <enter>,
then enter password when sudo asks for password, then press enter again.

Tip: If you have a wheel mouse or 3 button mouse you do not need to type commands into the Terminal. Highlight the command written on the page. Move your cursor anywhere in the Terminal and press the wheel or middle button. Automatic Copy and paste! No spelling mistakes! No Typos! No other errors!

sudo apt-get update; sudo apt-get install hwinfo grep; sudo lshw -C network; rfkill list; sudo iwlist scanning; cat /etc/network/interfaces; cat /etc/lsb-release; lspci -nn; lsusb; sudo lshw -short; uname -a; dmesg | egrep 'ound|irmware|eth|ath|wl|ipw|rtl|rt2|b43|witch|ndiswrapper'; iwconfig; grep b43 /etc/modprobe.d/*; grep wl /etc/modprobe.d/*; sudo hwinfo --netcard ; sudo lsmod; sudo /etc/init.d/networking restart

Step 4: Please post results (copy/paste terminal output) on this thread. The troubleshooters here need to see the full Terminal output from running the above command.

Step 5: Step 4: Please also specify the exact model and make of your PC (if known).

----------------------------------------------------------------------------------------
New to Ubuntu: read the Ubuntu Manual, it's very informative: http://ubuntu-manual.org/
Click on the "download Button" to download the latest PDF version.
The online help https://help.ubuntu.com/10.04/index.html

Relax and fun:
http://planet.ubuntu.com/ and Full Circle Magazine http://fullcirclemagazine.org/