Wet String Transmission Line

The wet strings are equivalent to uninsulated wires carrying ~4800 volts AC — potentially lethal. DO NOT touch them with bare hands. DO NOT allow them to touch each other. Keep students at a safe distance. Have a readily accessible power cutoff.

Strings dry out over time, increasing resistance. For multiple presentations, keep backup strings soaking in salt water.

Do not allow wet strings to touch each other — this can damage transformers and cause arcing. Use a power strip with an accessible switch for emergency shutdown.

Purpose

Demonstrates why power lines use high voltage. Transformers step 110V up to ~4800V to transmit power through high-resistance wet strings, then step back down to light a bulb. Direct connection at 110V fails -- showing that $P_{loss} = I^2R$ favors high voltage (low current) for transmission.

Two demountable transformers on metal stands connected by wet strings draped between them, with coils on wooden bases and an illuminated light bulb on the right; chalkboard with generator equations behind

Figure 1: Complete setup: step-up transformer (left), wet saline strings as transmission lines, and step-down transformer (right) powering an illuminated light bulb.

Small Photographic Tray

1

String with Connectors

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Danger: High Voltage Hazard

Warning: String Maintenance

Warning: Electrical Safety

Purpose

Safety Warnings

Danger: High Voltage Hazard

Warning: String Maintenance

Warning: Electrical Safety

Purpose