In a series circuit, changing a single resistor affects the entire system. Slide the control to increase the resistance of Resistor 2 (R2) while leaving R1 and R3 constant.
Observe the matrix carefully: What happens to the total current (I) everywhere? What happens to the specific voltage drop across R2?
Isolate & Adjust R2
10 Ω100 Ω
Observation Tracker
Total Current (I): ---
Voltage Drop (V2): ---
12V
R1
R2
R3
Component
Resistance (R)
Current (I)
Voltage Drop (V)
R1 (Fixed)
10.0 Ω
---
---
R2 (Variable)
10.0 Ω
---
---
R3 (Fixed)
10.0 Ω
---
---
TOTAL (Circuit)
30.0 Ω
---
12.00 V
Elaborative Interrogation
Look at the matrix. As you increase the resistance of R2, the total current flowing through the circuit decreases. However, the voltage drop across R2 actually increases. Why does V2 go up if the current pushing through it is going down?
Because R2 is taking a larger "slice" of the total resistance! Even though total current (I) is decreasing, the resistance of R2 is increasing at a faster proportional rate. Since V = I × R, the voltage drop across R2 grows, taking a larger share of the 12V source away from R1 and R3.