The electrified carpet that is covered in bits of cold and coins and notes is something that the whites in this terrible extract dream up for their own amusement after the boxing match. The sight of the black boys experiencing multiple electric shocks and then also laughing to try and distract themselves as they gather up money is truly pitiful, especially in the way that the text describes it:
Laughing embarrassedly, we struggled out of their hands and kept after the coins. We were all wet and slippery and hard to hold. Suddenly I saw a boy lifted into the air,
glistening with sweat like a circus seat, and dropped, his wet back
landing flush upon the charged rug, heard him yell and saw him literally dance upon his back, his elbows beating a frenzied tattoo upon the floor, his muscles twitching like the flesh of a horse stung by many flies. When be finally rolled off, his face was gray and no one stopped him when he ran from the floor amid booming laughter.
Clearly, the sadistic implications of this scene are rather disturbing when we consider how the whites are enjoying the torture of these black boys, and the racial overtones of the scene make it even more disturbing. However, you might like to consider the significance of what is happening and how it acts as a symbol of white-black interaction at the time. The blacks are forced to experience pain and embarrassment as they try and get the coins that are available to them for the amusement of the whites. They are in a situation where they have to demean themselves to make a living, which is of course exactly what African-Americans had to do back then.