PhysicsChapter 11: Electricity

Single-Loop Circuits

A single-loop circuit has no junctions. Charge has only one route, so every series component carries the same current.

Solution method

Choose a current direction.
Add all series resistances.
Write one loop equation using consistent signs.
Solve for current, then calculate individual voltage drops.
Check that the complete loop gives zero net potential change.

Key equation

R_eq=R₁+R₂+⋯

Key equation

I=εR_eq

Cell with internal resistance

Key equation

ε-I(R+r)=0

Key equation

I=εR+r

Key equation

V=ε-Ir=IR

Solved example

A 12 V cell with internal resistance 1.0 Ω is connected to 5.0 Ω:

Key equation

I=125.0+1.0=2.0\ A

Key equation

V=IR=(2.0)(5.0)=10\ V

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