15 Dust Cloud Ignition Caused due to Static Electricity A case study investigates the reasons behind the ignition of dust cloud during a manual powder processing About 18 kg of combustible powder was tipped from a plastic drum into a metal vessel The powder had minimum ignition energy of 12 m It was noticed that there was an ignition of dust cloud formed at the top of vessel due to pouring of powder To verify the theory of this ignition 18 kg of same powder was tipped from a similar drum into Faraday Cage Surface area of the chime was about 0 0641 m Total charge created by the movement of powder was 3 6 C The maximum charge density of surface in air is equivalent to 27 C per square metre The capacitance of chime was estimated to be 71 pf Using the above information and understanding of basic concepts of electrostatics answer the following 1 The cause of ignition is are a charging of powder due to friction c developed potential difference 2 The total charge density of the chime is a 27 C m c 72 C m 3 The maximum charge on the chime is a 1 7 x 10 C c 3 6 C 4 Voltage of the chime is a 2400 V c 24 KV 5 S I unit of charge density is a cm3 c Cm b 56 x 106C m d 65 x 10 C m b 7 1 x 10 C d 6 3 C Plastic drum with metal Chime Ring b 4200 V d 42 KV b C cm 2 d cm b induced charge on the metal drum d all of these