Measurement of conductivity. A method of measuring conductivity of fluids is to construct a cylinder and drill a hole at the center of the cylinder. Both ends are plugged with cylindrical plugs of known length and of the same conductivity as the cylinder (Figure 7.34a). Assuming the conductivity of the cylinder is σ0 and dimensions are as shown, calculate the resistance of the device. Now, one plug is removed and the hollow space is filled with fluid as shown in Figure 7.34b. If the resistance of the device is now lower by 10%, what is the conductivity of the fluid?
