University Physics Volume 2

# Key Equations

### Key Equations

 Displacement current $Id=ε0dΦEdtId=ε0dΦEdt$ Gauss’s law $∮E→·dA→=Qinε0∮E→·dA→=Qinε0$ Gauss’s law for magnetism $∮B→·dA→=0∮B→·dA→=0$ Faraday’s law $∮E→·ds→=−dΦmdt∮E→·ds→=−dΦmdt$ Ampère-Maxwell law $∮B→·ds→=μ0I+ε0μ0dΦEdt∮B→·ds→=μ0I+ε0μ0dΦEdt$ Wave equation for plane EM wave $∂2Ey∂x2=ε0μ0∂2Ey∂t2∂2Ey∂x2=ε0μ0∂2Ey∂t2$ Speed of EM waves $c=1ε0μ0c=1ε0μ0$ Ratio of E field to B field in electromagnetic wave $c=EBc=EB$ Energy flux (Poynting) vector $S→=1μ0E→×B→S→=1μ0E→×B→$ Average intensity of an electromagnetic wave $I=Savg=cε0E022=cB022μ0=E0B02μ0I=Savg=cε0E022=cB022μ0=E0B02μ0$ Radiation pressure $p={I/cPerfect absorber2I/cPerfect reflectorp={I/cPerfect absorber2I/cPerfect reflector$