Can someone explain to me how they work?
I know they work off your energy, but I sometimes have a negative energy on a question I ask and it still says yes as a response...
Also can you frequently ask the same question?
Many people have different theories on how they work. One theory is your communicating with some type of spirit or entity while another is your unconsciously moving the pendulum yourself. These are only two out of many theories. The second theory I mentioned or both also fit with how people tend to believe a Ouija board works. The second theory might seem like you'd give yourself the answer you want instead of a prediction, but some believe your tapping into your psychic abilities and it's a sorta way to train your intuition or psychic ability. Like I say these are only theories. I personally own a pendulum, but have yet to receive a reliable prediction from it, but I don't practice much.
Your hand naturally moves from your pulse and this makes the pendulum move. The belief is that these movements have something to do with the question your asking. So in theory no matter how many times you ask a question it should come up with the same answer.
Oh and to your multiple question question most people say not to ask a question multiple times. One reason is if it's a spirit or entity you'd aggregate it, but also it could be the pendulum might give conflicting answers. I guess it depends on how it works. I recently read something about getting answers from a demon or communicating with one by swinging the pendulum of a demon's sigil. Probably not something you'd want to try, but that's an example of getting your answers via a entity.
I don't know about the benefit of getting a friend to ask the same question, but the pulse issue goes back to whether or not your harnessing your intuition or psychic ability and your pulse is just the means it uses to move the pendulum.