Lets say you have a SharePoint group named "Notify Members". They would like to receive an alert when a document is added to the document library "Business document". Here are list of PowerShell Commands to achieve the functionality.
$web = Get-SPWeb "http://localhost/mysite/"$group = $web.Groups["Notify Members"]$list = $web.Lists[" Business document"]foreach ($user in $group.Users){ $alert = $user.Alerts.Add() $alert.Title = "Alerts" $alert.AlertType = [Microsoft.SharePoint.SPAlertType]::List $alert.List = $list $alert.DeliveryChannels = [Microsoft.SharePoint.SPAlertDeliveryChannels]::Email $alert.EventType = [Microsoft.SharePoint.SPEventType]::Add $alert.AlertFrequency = [Microsoft.SharePoint.SPAlertFrequency]::Immediate $alert.Update()}$web.Dispose()