LFM

Reading a circuit

Every circuit is a loop. Use the tabs to see the three things that loop can do, switch between working, open, and shorted, and click any part to read what that part is.

I = 23 mA + BT15 V SW1 R1220 Ω
Click the battery, switch, or resistor
Loop current23 mA
State

A complete loop

I = 10 mA (everywhere) + BT15 V R1200 Ω drops 2 V R2300 Ω drops 3 V
Click R1 or R2
Current through both10 mA
One path

Series: one shared path

R1 and R2 sit one after the other on a single path, so the same current flows through both. The total resistance is 200 + 300 = 500 Ω, so I = 5 / 500 = 10 mA. The voltage splits between them in proportion: 2 V across R1, 3 V across R2, adding back to the 5 V source.
+ BT15 V R1100 Ω R2200 Ω
Click R1 or R2
R1 branch (100 Ω)50 mA
R2 branch (200 Ω)25 mA
Total from source75 mA
Two paths

Parallel: the current splits

R1 and R2 each have their own path from the source, so the full 5 V appears across each. Each draws its own current by Ohm's law: 5 / 100 = 50 mA through R1 and 5 / 200 = 25 mA through R2. The source supplies both, so it delivers 50 + 25 = 75 mA. The smaller resistor draws the larger current, and cutting one branch does not change the other.