Conducting Putty. Conducting putty is useful aid to teaching resistivity and the relationship between length and cross-sectional area on resistance. cylinder 60mm long and 20mm in diameter has resistance of approximately 20Ω. Can readily be connected into an electrical circuit and both length and diameter can easily be altered by 're-moulding' the putty. Although harmless, plastic gloves are provided to prevent hands from becoming stained. Approx. 100g.