# Kirchhoff and Potential Dividers

Energy is conserved in all circuits, for any complete circuit the sum of the emfs is equal to the sum of the potential differences.

Energy givers = energy takers.

In the diagram we can say that:                                        ε = pd1 + pd2 + pd3 + pd4.

# Uses

In this potential divider the second resistor is a thermistor. When the

temperature is low the resistance (R2) is high, this makes the output voltage

high. When the temperature is high the resistance (R2) is low, this makes the

output voltage low. A use of this would be a cooling fan that works harder

when it is warm.

In the second potential divider the second resistor is a Light Dependant Resisitor.

When the light levels are low the resistance (R2) is high, making the output voltage

high. When the light levels increase the resistance (R2) decreases, this makes the

output voltage decrease. A use of this could be a street light sensor that lights up

when the surrounding are dark.