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MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Department of Electrical Engineering and Computer Science
6.013 – Electromagnetics and Applications
Problem Set 3 (four problems)
Suggested Reading:
Course notes, Sections 3.1.3, 3.2, 5.15.2, 5.4, and 6.16.2
.
Problem 3.1
Two parallel metal plates separated by d
overlap a distance b and have width L; they
are charged to a voltage V.
(a)
What is the force f
⊥
[N] attracting the two plates in the y direction?
(b)
What is the force f
//
[N] attracting the two plates in the x direction?
(c) Suppose we wish to design an electrostatic motor.
To minimize losses associated with
fringing fields the plate separation d should be less than ~ b/4 and L/4.
To prevent
arcing, the electric field strength E should be less than the air breakdown field strength
E
bd
. Assume that practical considerations limit the maximum velocity of motor parts
to about 100 m/s, or roughly onethird the velocity of sound, and limit the minimum
plate separation to ~0.5 mm.
Based on these constraints, what is roughly the
maximum mechanical power P
max
[Watts] we can obtain from a cleverly designed
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This note was uploaded on 02/02/2012 for the course EE 013 taught by Professor Staelin during the Spring '09 term at MIT.
 Spring '09
 staelin
 Electromagnet

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