Physics Book Solutions

# 3g1 785 233g1036788 8 925

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: stant by ! # K !0 . The maximum voltage is E0 = # , where K K !0 = is the surface charge density on each plate. The induced surface charge density on the surface of the dielectric is given by = i # = (1 ! 1/ K ) . SET UP:! From Table 24.2, for polystyrene K # 2.6 and the dielectric strength (maximum allowed electric field) is 2 &quot; 107 V/m . EXECUTE:! (a)! ! # K !0 # (2.6)!0 # 2.3 &quot; 10!11 C2 N + m 2 related to the maximum possible electric field before dielectric breakdown by Vmax # Emax d . E # (b) Vmax # Emax d # (2.0 &quot; 107 V m)(2.0 &quot; 10!3 m) # 4.0 &quot; 104 V (c) E # % ) = K !0 and = # !E # (2.3 &quot; 10!11 C2 /N + m2 )(2.0 &quot; 107 V/m) # 0.46 &quot; 10!3 C/m2 . 1&amp; * = i # = '1 ! ( # (0.46 &quot; 10!3 C/m 2 )(1 ! 1/ 2.6) # 2.8 &quot; 10!4 C/m 2 . K EVALUATE:! The net surface charge density is = net # = ! = i # 1.8 &quot; 10!4 C/m 2 and the electric field between the plates is E # = net / !0 . 24-12 Chapter 24 24.44. IDENTIFY:! C # Q / V . C # KC0 . V # Ed . SET UP:! Table 24.1 gives K # 3.1 for mylar. EXECUTE:! (a) BQ # Q ! Q0 # ( K ! 1)Q0 # ( K ! 1)C0V0 # (2.1)(2.5 &quot; 10!7 F)(12 V) # 6.3 &quot; 10!6 C . 24.45. (b) = i # = (1 ! 1/ K ) so Qi # Q(1 ! 1/K ) # (9.3 &quot; 10!6 C)(1 ! 1/ 3.1) # 6.3 &quot; 10!6 C . (c) The addition of the mylar doesn’t affect the electric field since the induced charge cancels the additional charge drawn to the plates. EVALUATE:! E # V / d and V is constant so E doesn't change when the dielectric is inserted. (a) IDENTIFY and SET UP:! Since the capacitor remains connected to the power supply the potential difference doesn’t change when the dielectric is inserted. Use Eq.(24.9) to calculate V and combine it with Eq.(24.12) to obtain a relation between the stored energies and the dielectric constant and use this to calculate K. EXECUTE:! Before the dielectric is inserted U 0 # 1 C0V 2 so V # 2 2 .1.85 &quot; 10!5 J / 2U 0 # # 10.1 V C0 360 &quot; 10!9 F (b) K # C/C0 U 0 # 1 C0V 2 , U # 1 CV 2 so C/C0 #...
View Full Document

## This document was uploaded on 03/11/2014 for the course PHYSICS 240 at University of Michigan.

Ask a homework question - tutors are online