Sunday's big game between the Indianapolis Colts and Chicago Bears marked the first-ever rainy Super Bowl. Prince's high-tech halftime show had viewers and critics raving, but all that equipment and rain looked like an electrocution waiting to happen. How do you keep soaking-wet performers from getting shocked?
You go wireless. The use of battery-powered, wireless equipment provides one measure of safety; performers and their crews should also check to make sure that any stray electrical current goes into the ground, and that they've set up a way to shut off power in an emergency. These safety procedures are standard practice when there's a lot of electrical equipment around, but they're particularly important when it's raining. Our susceptibility to electrical shock is greatly increased when our skin is wet—whether we're soaked with rain, or just a little sweaty. (Dry skin acts as a stronger resistor and can protect us from small shocks.)
Battery-powered wireless microphones, guitars, and other gear keep performers isolated from potentially dangerous electrical current. To get a shock, you have to become part of an electrical circuit between a high-voltage source—like a power line—and the ground (or a grounded object, like a ladder). Without coming into contact with both, you can't be electrocuted, which is why birds on power lines don't get fried. It's also one of the reasons why wireless equipment keeps performers safe in the rain—if you're not physically connected to the current, you can't get shocked. If wireless equipment isn't available, the use of low-voltage equipment can also reduce the risk of shock.
The proper grounding of electrical equipment can help protect anyone working behind the scenes, like sound engineers or camera operators, from possible shocks. (In 1976, musician Keith Relf of the Yardbirds died because his guitar wasn't grounded properly.) An assured grounding program involves two tests, both of which can be conducted with an ohmmeter to measure electrical resistance. The first test makes sure that there are no gaps in the electrical setup that could let current leak out and shock someone. The second test makes sure that the equipment-grounding conductor, which carries any extra current to the ground, is sending the electrical flow to the right place. Whether it's raining or not, making sure that equipment is grounded—that any stray current will go directly into the earth instead of into the poor sound guy who touches the wrong wire—is an important safety precaution. (Three-pronged electrical plugs, which refrigerators and other equipment often have, also ground the current.)
If an electrical shock does occur, devices called "ground fault circuit interrupters" can prevent a fatality. A GFCI works by measuring the amount of current going into a circuit and the amount of current coming out. In general, these two readings should be the same; if they're not, there must be a leak somewhere along the line, which could indicate that a person is getting shocked. * The GFCI, which costs about $10 for household use and is standard-issue on blow dryers, automatically shuts down the power when it senses a leak. The person might still feel the shock, but it probably wouldn't be fatal.
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Explainer thanks Michael Morse of the University of San Diego and Mitch Ricketts of Kansas State University.