physics_current_electricity
 Current Electricity Ohm's LawVβR$V\beta R$V=IR$V=IR$ Drift Velocityvd=-eEm π${v}_{d}=-\frac{eE}{m}\phantom{\rule{0.22em}{0ex}}\mathrm{\pi }$ where π$\mathrm{\pi }$=relaxation timeE=electric fieldm=mass of electron Current density=jj=ne2m π E$j=\frac{n{e}^{2}}{m}\phantom{\rule{0.22em}{0ex}}\mathrm{\pi }\phantom{\rule{0.22em}{0ex}}E$ Resistance=R=πlA$=R=\mathrm{\pi }\frac{l}{A}$ where, π=$\mathrm{\pi }=$Resistivity of material Conductivity=π=1π$=\mathrm{\pi }=\frac{1}{\mathrm{\pi }}$ Mobility (π)$\left(\mathrm{\pi }\right)$ is defined as magnitude of the drift velocity per unit electric field.π=| vd |E$\mathrm{\pi }=\frac{|\phantom{\rule{0.22em}{0ex}}{v}_{d}\phantom{\rule{0.22em}{0ex}}|}{E}$ Ammeter: The resistance of Ammeter must be very small compared to other resistances in the circuit. A galvanometer can be converted into Ammeter by connecting a resistor of very low resistance R in parallel. Voltmeter: A galvanometer can be converted into voltmeter by connecting a resistor of high resistance R in series.
 QWhat is Specific resistance ASpecific resistance of a conductor is defined as the resistance offered by conductor per unit length and unit cross-sectional area when the known amount of voltage is applied.Specific Resistance=π=RAL$=\mathrm{\pi }=\frac{RA}{L}$ where,π=$\mathrm{\pi }=$Resistivity of materialR: resistanceA: cross-sectional areaL: length of the material QWhich conservation principle is involved in Kirchoffβs second law?AKirchhoffβs second law or voltage law is a consequence of the law of conservation of energy.