Lecture_07 - Electric Potential Energy of Two Particles...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
q 1 q 2 r 12 ! E 1 + ! E 2 " W int = W ext Δ U el - W int ! K system + ! U el = W ext + Q Total energy of the system can be changed ( only ) by external forces. Work done by internal forces: Electric Potential Energy of Two Particles Energy of the system: 1. Energy of particle q 1 2. Energy of particle q 2 3. Interaction energy U el To change the energy of particles we have to perform work. ! E 1 + ! E 2 = W ext + W int + Q if ! ( mc 2 ) = 0 : Energy Principle for a multiparticle system. ! U el = " W int = " ! F int d ! l i f #
Background image of page 1

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

View Full DocumentRight Arrow Icon
Example An electron traveling to the right enters capacitor through a small hole at A. Electric field strength is 2x10 3 N/C. What is the change in the electron ` s potential energy in traveling from A to B? What is its change in kinetic energy? Δ ( AB)= 4mm = (1.6x10 -19 C)(2x10 3 N/C)(0.004m) =1.3x10 -18 J Δ K = . Δ U electric = -1.3x10 -18 J x ! U electric = " ! F i ! ! l = " ( " eE x ) ! x = eE x ! x
Background image of page 2
Electric potential electric potential energy per unit charge Units: J/C = V (Volt) Electric potential, V – often called potential Electric potential difference, Δ V – often called voltage Electric Potential Difference in a Uniform Field Volts per meter = Newtons per Coulomb ! U electric = q ! V , ! V = ! U electric q
Background image of page 3

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

View Full DocumentRight Arrow Icon
! V = " ! E i ! ! l = " ( E x ! x + E y ! y + E z ! z ) If we multiply through by q , we recover the relation between the change in potential energy and work done on q by the internal force.
Background image of page 4
30 0 ! V = " ! E
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/13/2012 for the course PHYS 272 taught by Professor K during the Spring '07 term at Purdue University-West Lafayette.

Page1 / 20

Lecture_07 - Electric Potential Energy of Two Particles...

This preview shows document pages 1 - 6. Sign up to view the full document.

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