each and this not working?

each and this not working?

why does this not work? it says undefined. If i do $('input').val(); outside of the each then it will work its like the $('this') is not working. Please help.

<!DOCTYPE HTML>
<html lang="en-US">
<head>
    <meta charset="UTF-8">
    <title></title>
    <link rel="stylesheet" href="style.css" />
</head>
<body>
   
    <div class="wrapper">
        <form action="">
            <label for="tags">Enter Some Tags, Bro.</label>
            <input type="text" value="wer" />
            <input type="text" class="tags" value="asdf" />
        </form>
    </div>
   
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.2/jquery.min.js"></script>
<script type="text/javascript" src="tags.jquery.js"></script>
<script type="text/javascript">
    $(document).ready(function(){
        $('input').each(function(){
            alert($('this').val());
        });
    });
</script>   
</body>
</html>