Electrostatics: Electric Charges, Electric Field, Potential and Capacitors - Prof. Kamil U, Study notes of Physics

Download Electrostatics: Electric Charges, Electric Field, Potential and Capacitors - Prof. Kamil U and more Study notes Physics in PDF only on Docsity! Overall Story Protons and electron carry charge Presence of charge creates an electric field The field creates potential differences between points within the space it exists Other charges react to this field and potential and move about (current) Electrical Charges Charge is carried by electrons and protons. Can be positive or negative. Like charges repel, opposite charges attract. Total charge in a system is conserved. Charges come in discrete quantities. Charges are measured in Coulombs (C). Usually denoted by q. ∫=Φ surface E A.dE vv 0 . ε in E qd ==Φ ∫ AE rv Electric Flux Gauss’ Law Gauss’ Law 2r QkE e= r > a r < R r a QkE e ⎟ ⎠ ⎞ ⎜ ⎝ ⎛= 3 02ε σ =E r E 02πε λ = Conductors and Gauss’ Law The electric field is zero everywhere inside a conductor at electrostatic equilibrium. Any net charge on a conductor will reside on the surface. The electric field just outside a conductor is perpendicular to the surface and is proportional to the charge density. The charge density is highest near parts of the conductor with the smallest radius of curvature. 0ε σ =E ∫−=Δ B A dqU sE rv .0 ∫−= Δ =Δ B A d q UV sE v v . 0 Potential Difference EdV −=Δ r qkV e= x VEx ∂ ∂ = z VEz ∂ ∂ = y VEy ∂ ∂ = ∫= r dqkV e Electric Potential Energy In a Uniform Field For a Point Charge For a Charge Distribution Electric Potential dt dQtI =)( EJ σ= I VR Δ= σ ρ 1= A lR ρ= ( )[ ]00 1 TTRR −+= α ( ) R VRIVI 2 2 Δ==Δ=P Current and Resistance DC Circuits ∑= i ieq RR ∑= i ieq RR 11 ∑∑ = junction out junction in II 0=Δ∑ loop closed V ( ) ( )RCtRCt eQeCtq −− −=−= 11)( E RCte Rdt dqtI −== E)( RCt RCt e RC Q dt dqtI Qetq − − −== = )( )( Series Parallel Kirchoff’s Rules RC Circuits