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ECE 2317 Applied Electricity and Magnetism. Prof. D. Wilton ECE Dept. Notes 5. Notes prepared by the EM group, University of Houston. Grounding. Grounding: connecting a conductor to the physical earth. Safety reasons Noise reasons. equipment. water pipe. equipment. +. V AB = 0.
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ECE 2317 Applied Electricity and Magnetism Prof. D. Wilton ECE Dept. Notes 5 Notes prepared by the EM group, University of Houston.
Grounding Grounding: connecting a conductor to the physical earth • Safety reasons • Noise reasons equipment water pipe
equipment + VAB = 0 - water pipe Grounding (cont.) • Ensures that there is no voltage drop between equipment and ground • Ensures that there is no electric field outside of equipment • Ensures that there is no charge build up on equipment
equipment ground Grounding (cont.) Ground symbol: Note: grounding is NOT is the same thing as a reference point. (However, when a circuit is grounded, the ground is OFTEN chosen as a reference point of zero volts.)
A + 12 [V] 100 - B ground Example reference point (choose 0 [V]) Find: voltage at the ground VG
Grounding (cont.) hot neutral (grounded back at junction box) ground
Grounding (cont.) wall I hot + junction box V - neutral ground The neutral wire is grounded back at the junction box. Note: The voltage of the neutral wire at the device is not the same as ground, because the neutral wire has a resistance.
Ground Protection The metal casing of an electrical device is normally connected to ground. hot neutral ground
GFCI (Ground Fault Circuit Interrupter) Ih Ig = Ih - In hot neutral In GFCI Circuit trips when Ig > 5 [mA]
Double Insulated Tool Ih plastic case hot neutral In The device is surrounded by an insulating plastic case. It does not require a ground.