Usage of [0] with visual effects in jquery
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Why selecting via [0] in jquery does not work with visual effects??

    $("p")[0].slideUp(); /* it does not work*/
    $("p").eq(0).slideUp(); /* it works */
    
As mentioned, I know there are some other ways to select the first p, but I am eager to know why the above mentioned code is not working... 

Thanks in advance,