Evaluation of The Effect of Moisture Content on The Electrical Resistance of Poplar Wood at Constant Temperatures

In order to evaluate the effect of moisture content (MC) on the electrical resistance (R) of poplar wood, three poplar trees (P. deltoeides) were selected and harvested in the Shast Kalateh forest in Gorgan, and eight matched clear specimens with dimensions of 27/510 cm were taken from each one. The electrical resistance and the corresponding internal temperature values of each specimen were measured simultaneously with a gradual increase in temperature between 15-100 oC, separately. The test was repeated for several turns and all of the specimens were weighed at the beginning and end of each run. All of the specimens were oven-dried with temperature of 103±2 oC for 24 hours at the end of the test to calculate the MC values corresponding to each electrical resistance and internal temperature values of each specimen with assuming the linear changes of MC of wood during each run of testing. The analysis of variance (ANOVA) at the 95% confidence level by SPSS14 software showed that the difference between different temperature values was significant, and electrical resistance decreased at a constant MC by the increase of temperature. Thus, eight linear models were evaluated to determine relationship between MC and electrical resistance at different temperature values, separately. According to the ANOVA test of the correlation coefficient, the best equation was chosen and moisture content-electrical resistance curves at different temperatures were drawn based on it. The results have shown that the electrical resistance decreases with increasing of moisture content at all temperature values with a same slope, but the slope of the curve decreases at the high temperature values (close to 100 oC).