Potential divider with variable load
A potential divider circuit where the load resistance can change (e.g., a thermistor or LDR as the load). The output voltage depends on both the divider ratio and the load resistance, making it useful for creating circuits sensitive to temperature or light.
Formula
V_out = V_in × R₂/(R₁ + R₂) (no-load); effective R₂ = R₂||R_L under load
Real World
The ambient light sensor in an iPhone uses an LDR in a potential divider: as the room dims, the LDR's resistance rises, shifting V_out and automatically reducing screen brightness.
Exam Focus
When a load is connected, always calculate the parallel combination of R₂ and R_L first before applying the divider formula.
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