Physics

# Key Equations

PhysicsKey Equations

## 19.1Ohm's law

 electric current I is the charge $ΔQ ΔQ$ that passes a plane per unit time $Δt Δt$ $I= ΔQ Δt I= ΔQ Δt$ an ampere is the coulombs per unit time that pass a plane $1A=1C/s 1A=1C/s$ Ohm’s law: the current I is proportional to the voltage V, with the resistance R being the constant of proportionality $V=IR V=IR$

## 19.2Series Circuits

 the equivalent resistance of N resistors connected in series $R equiv = R 1 + R 2 +⋯+ R N R equiv = R 1 + R 2 +⋯+ R N$

## 19.3Parallel Circuits

 the equivalent resistance of N resistors connected in parallel $R equiv = 1 1/ R 1 +1/ R 2 +⋯+1/ R N R equiv = 1 1/ R 1 +1/ R 2 +⋯+1/ R N$

## 19.4Electric Power

 for a given current I flowing through a potential difference V, the electric power dissipated $P=IV P=IV$ for a given current I flowing through a resistance R, the electric power dissipated $P= I 2 R P= I 2 R$ for a given voltage difference V across a resistor R, the electric power dissipated $P= V 2 R P= V 2 R$