Potential Divider Principle

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By increasing the resistance of R1 or decreasing the resistance of R2, the Vout will be increased.

Sometimes, R1 or R2 are replaced by thermistors or light-dependent resistors (LDR)

• Thermistors’s resistance normally decreases as temperature increases.
• LDR’s resistance decreases as light intensity falling on them increases.

Potentiometer uses the potential divider principle to measure potential differences and e.m.f.

The unknown potential difference OR e.m.f., VAB is applied across point A and B, with the point at higher potential connected to A.

Then J is moved along XY until a point Z where no current flows through the galvanometer (the galvanometer shows no deflection). This is the balance point where VAB is equal to VXZ. Then LXZ is known as the balance length.

$V_{AB} = V_{XZ}$

$V_{AB} = \frac{L_{XZ}}{L_{XY}} V_{XY}$

$\frac{V_{XZ}}{V_{XY}} = \frac{R_{XZ}}{R_{XY}}$

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