wp_enqueue_script('slider', plugins_url( 'slider.js', __FILE__ ) );

$(document).ready(function () {
    alert("alert");
});

wp_deregister_script('jquery');
wp_register_script('jquery', "http" . ($_SERVER['SERVER_PORT'] == 443 ? "s" : "") . "://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js", false, null);
wp_enqueue_script('jquery');

wp_enqueue_script( 'slider', plugins_url( 'slider.js', __FILE__ ),array('jquery') );

(function($) {
  $(function() {
    // more code using $ as alias to jQuery
  });
})(jQuery);