In case, for some reason, you need to change the name of your web application after it’s created, it’s very easy to do in SharePoint Powershell.

Create a new text file with the ‘.ps1′. extension. In it, put in these 3 lines:

$OldSolution =Get-SPWebApplication | where {$_.Name -match "<OldWebApp>"}
$Old.Name="<NewWebAppName>"
$Old.Update()

Open up PowerShell, change the directory to where you copied the new file and type in:

.\<YourFileName>.ps1

Even though this changes the Web Application name, it does not change the URL assigned to it at the time of creation (assuming you’re not using Host Headers). To change the URL, just go to Central Administration/System Settings/Configure alternate access mappings, under Farm Management. From there, click on each one you want to change and type in the new url in the ‘URL protocol, host and port’ textbox and click ok. That’s all there is to it