University Physics Volume 2

# Key Equations

### Key Equations

 Average electrical current $Iave=ΔQΔtIave=ΔQΔt$ Definition of an ampere $1A=1C/s1A=1C/s$ Electrical current $I=dQdtI=dQdt$ Drift velocity $vd=InqAvd=InqA$ Current density $I=∬areaJ→·dA→I=∬areaJ→·dA→$ Resistivity $ρ=EJρ=EJ$ Common expression of Ohm’s law $V=IRV=IR$ Resistivity as a function of temperature $ρ=ρ0[1+α(T−T0)]ρ=ρ0[1+α(T−T0)]$ Definition of resistance $R≡VIR≡VI$ Resistance of a cylinder of material $R=ρLAR=ρLA$ Temperature dependence of resistance $R=R0(1+αΔT)R=R0(1+αΔT)$ Electric power $P=IVP=IV$ Power dissipated by a resistor $P=I2R=V2RP=I2R=V2R$