kendo-ui - How to find selected tab on KendoTabStrip on page load?

Question

I am using Kendo UI MVC and i have a kendoTabStrip on acshtml page. By default I am selecting the first tab on page load. All other tabs are loaded dynamically using AJAX. Issue: I am trying to find the selected tab so i can find its children? one way to find active tab is by calling select() method without parameter, or anotherway is by checking classname 'k-state-active' however both methods doesnt work

<section class="tpt-tabstrip">
    @(Html.Kendo().TabStrip()
    .Name("MyTabStrip")    
    .Animation(false)    
    .Items(items =>
    {
        foreach (var revision in Model.MyCollection)
        {
            items.Add()
            .Text(revision.Name)
            .LoadContentFrom("MyActionMethod", "MyController", Model.ID);
        }
    })
    )    
</section>
<script src="~/Scripts/MyScript.js"></script>

Note that above in cshtml that the script tag is at the end of the page.
Below is the script code

$(function(){       
    var tabStrip = $("#MyTabStrip").getKendoTabStrip();
    if (tabStrip != null && tabStrip.tabGroup.length > 0) {
        tabStrip.select(0); // this line is getting executed for sure
    }

    // the line below returns -1 here why?????
    var index = tabStrip.select().index(); 

    // another way to find active tab is by checkikng class name 'k-state-active' however it didnt work either. 
    // jQuery couldnt find any element with class 'k-state-active'
    $('.k-state-active')
})

UPDATE1
The activate event of tabstrip would not work for me because it get fired each time i select tab. I need an event which gets fired only once. Ultimately i want to find NumericTextBox controls on selected tab and attach 'change' event handlers to those controls. like below

$(function(){
    var tabStrip = $('#MyTabStrip').data("kendoTabStrip");
    tabStrip.bind('activate', function (e) {
       $('[data-role="numerictextbox"]').each(function(){
           $(this).getKendoNumericTextBox().bind("change",function(e){
              alert('changed');
        })
       })
    });
})

here the change event handler will get attach to NumericTextBox everytime i select the tab