Current or Voltage: What Makes Electricity Dangerous?

0:00Is it voltage or current that makes electricity dangerous?

0:05If your body touches two parts of a live circuit, it becomes part of the circuit.

0:10Voltage, measured in volts, is the push that drives charge around a circuit.

0:16Current is the flow of charge, measured in amperes. One milliampere is a thousandth of an ampere.

0:24Resistance, measured in ohms, opposes the flow, and your body has resistance too.

0:31The harm comes from the current through your body, here across your chest.

0:37About 1 milliampere can be felt.

0:4010 to 20 milliamperes can lock your muscles, so you cannot let go.

0:45About 100 milliamperes across the chest can disrupt the heartbeat.

0:50Voltage matters because it pushes the current: current equals voltage divided by resistance.

0:57Dry skin is about 100,000 ohms, so 120 volts pushes about 1.2 milliamperes. You would feel it.

1:08Wet skin can drop to about 1,000 ohms. Now 120 volts pushes about 120 milliamperes, enough to disrupt the heartbeat.

1:18The voltage stayed the same, but lower resistance let a hundred times more current flow.

1:24So low voltage is not always safe. With wet skin, even a smaller voltage can push a harmful current.

1:33A static shock can be thousands of volts, but its charge is so tiny that the current stops almost at once.

1:41Current does the harm, and voltage matters because it drives that current through your body's resistance.