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Physics

Key Equations

PhysicsKey Equations

19.1 Ohm'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

19.2 Series 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

19.3 Parallel 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

19.4 Electric 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
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