In order to create a jQuery UI object, you need to capture the page load event.
Here is one way to achieve this:
<script type="text/javascript>
$(document).ready(function() {
var popUpList = $('<div><input type="radio" name="a">A<br><input type="radio" name="a">B<br><input type="radio" name="a">C</div>');
$("#dialog").click(function () {
popUpList.dialog();
});
});
</script>
Alternatively, you can also use:
<script type="text/javascript>
$(function(){
// This code block will be executed once jQuery has finished loading and is ready for use.
});
</script>