Check a check box is checked or not using jquery

I want to check a checkbox is checked or not using jquery. When click on the check box, check the checkbox is checked or not using jquery. My code is given below.

   <script>
   function check(id)
    {
     if($("#id:checked").length == 1)
      {
        alert("cheked");
      }
    }
   </script>


     Html
     $i=1;
     <input name="" type="checkbox" value="" 
     id="one<?php echo $i; ?>"  onclick="check(one<?php echo $i; ?>)"/>