dc circuits

Relationship between charge and current

I=\frac{dQ}{dt}

Q=\int_0^{t}I\,dt ——> Q=It

Voltage

V=IR

Kirchhoffs laws

• the sum of the currents flowing into a junction is equal to the currents flowing out

• the sum of the voltages around any closed loop must equal zero

Power supplied to a circuit

P=IV

Power dissipated in a resistor

P=IV=\frac{V^2}{R}=I^2R

Internal resistance

V=\varepsilon-rI