Powerline workers are exposed to high voltages; safe contact with high voltage circuits can only be made when the resistance between the circuit and a person is high enough to prevent which?

• A. power flow
• B. current flow
• C. watt usage
• D. voltage flow

Answer: (B)

The key idea is that safety hinges on limiting the current that can pass through a person. Ohm’s law tells us current through the body is I = V/R. If the resistance between the circuit and the person is kept high, the current is reduced to a level that’s not harmful. Voltage provides the push, but it’s the current that causes injury, so preventing or greatly reducing current flow is what keeps contact safe. The other ideas (power flow, watt usage, voltage flow) aren’t the direct factor in protecting a person—the crucial factor is the amount of current that could pass through them, which is controlled by increasing resistance. Insulating tools, gloves, and barriers raise that resistance to keep current to safe levels.