# Circuit Problem

1. Feb 16, 2005

### Jacob87411

The student engineer of a campus radio station wants to verify the effectiveness of the lightning rod on the antenna mast. The unknown resistance Rx is in between points C and E. Point C is just right of the antenna and point E is true ground but is inaccessible for the direct measurement because this stratum is several meters below the Earth's surface. Two identical rods are driven into the ground at point A (left of the antenna) and B (right of C which is just right of the antenna.) introducing an unknown resistance Ry. The procedure is as follows: Measure the resistance R1 between points A and B, then connect A and B with a heavy conducting wire and measure R2 between points A and C. (A) Derive a formula for Rx in terms of the observable resistances, R1 and R2. (B) A satisfactory ground resistnace would be Rx < 2.0 Ohm. Is the grounding of the station antenna adequate if measurements give R1=13 Ohm and R2=6 Ohm

Really lost on how to set up the original circuit I guess...Once I have that it shouldnt be that bad

2. Feb 16, 2005

### learningphysics

Draw a picture first...

Then from the picture you should see be able to make out the circuit.
Hint: there are 3 resistors, and ground(E) is a common point to all 3.