MECH466-Lecture-7 - MECH 466 Microelectromechanical Systems...

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1 MECH 466 Microelectromechanical Systems University of Victoria Dept. of Mechanical Engineering Lecture 7: Electrostatic Sensors and Actuators May 31st, 2007 Mech 466, N. Dechev, UVic 2 Parallel Plate Capacitors Equilibrium Positions of Electrostatic Devices Pull-in Voltage Overview Mech 466, N. Dechev, UVic
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3 Parallel Plate Capacitors Consider an “ideal” parallel plate capacitor: Mech 466, N. Dechev, UVic A Where: A - Overlap area of two plates E - Electric Field d - distance between the two plates E d A dielectric material will occupy the space between the two plates: The ‘Relative’ electrical permitivity is defined as: The permitivity of the material is: Where , is the permitivity of free space (vacuum) 4 Parallel Plate Capacitors The capacitance between two plates is defined as: Mech 466, N. Dechev, UVic Stored Charge Electrostatic Potential = A E d The electric energy stored in the capacitor is:
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5 Parallel Plate Capacitors To obtain an expression for capacitance for the parallel pales, we can use Gauss’s Law, where the electric field: This can be substituted into the capacitance equation to obtain: Mech 466, N. Dechev, UVic 6 By measuring C accurately, we can sense changes in A (area), Permitivity, or d (distance between plates). For example, Permitivity of a material can be influenced by:
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This note was uploaded on 02/02/2010 for the course MECH 466 taught by Professor Dechev during the Summer '07 term at University of Victoria.

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MECH466-Lecture-7 - MECH 466 Microelectromechanical Systems...

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