School of Physics Lecture Demonstration Manual

Ei-2 Lecher Wires

Published: Tuesday 14 March 2006 - Updated: Tuesday 29 March 2011

Aim

To demonstrate standing electromagnetic waves on a transmission line consisting of a pair of parallel wires.

Apparatus

Diagrams

Click on pictures to enlarge.

Lecher Wires Diagram

Description

The output of the transmitter is connected to the co-axial input of the lecher wire apparatus. If the globe is moved along the wires the intensity will cycle through minimum and maximum intensity corresponding to the nodes and antinodes of the standing wave. The distance between nodes corresponds to a half wavelength.

The globe may be positioned at a node and if the end of the Lecher wires is shorted the globe will then indicate an antinode.

In the open circuit case the end must be an antinode (E field max).

In the short circuit case the end must be a node (E field zero).

Safety notes

Electrical safety 

Maintenance 

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