You can switch the polarity of the bar magnet by clicking on the button with the bar magnet and two semi-circular arrows on the bottom right. note how the positions of the north and south poles are switched every time you click on this button. drag the bar magnet from left to right through the top coil, then repeat the same process after switching the polarity of the magnet. what effect, if any, does switching the polarity have on the brightness of the bulb and the needle of the voltmeter?