hw7 - Physics 21 Fall, 2009 Solution to HW-7 24-25 A 5 . 80...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Physics 21 Fall, 2009 Solution to HW-7 24-25 A 5 . 80 F, parallel-plate air capacitor has a plate separation of 5 . 00 mm and is charged to a potential difference of 400 V. Calculate the energy density in the region between the plates, in units of J / m 3 . The equation for energy density without a dielectric material is given by u = 2 E 2 . The electric field in the region between the parallel plates can by found from the relation V = Ed . Solving for E and combining the equations yields u = 2 V d 2 . Inserting the numbers from the problem the calculation is u = 2 400 5 . 00 10- 3 2 = 2 . 83 10- 2 Jm- 3 . 24-38 A parallel-plate capacitor has capacitance C = 5 . 00 pF when there is air between the plates. The separation between the plates is 1.50 mm. (a) what is the maximum magnitude of charge Q that can be placed on each plate if the electric field in the region between the plates in not to exceed 3 . 00 10 4 V/m? (b) A dielectric with K = 2 . 70 is inserted between the plates of the capacitor, completely filling the volume between the plates. Now what is the max- imum magnitude of charge on each plate if the electric field between the plates is not to exceed 3 . 00 10 4 V/m? (a) Without the dielectric, Q = C V and V = Ed . There- fore, the charge for the given values of C , E , and d are Q = C Ed = ( 5 . 00 10- 12 F ) 3 . 00 10 4 V m ( . 0015 m) = 2 . 25 10- 10 C = 225 pC (b) With the dielectric, C increases to...
View Full Document

This note was uploaded on 11/06/2009 for the course PHYS 21 taught by Professor Hickman during the Spring '07 term at Lehigh University .

Page1 / 2

hw7 - Physics 21 Fall, 2009 Solution to HW-7 24-25 A 5 . 80...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online