the potential divider

What is a potential divider?

Two or more resistors in series with each other and with a source of fixed potential difference, where the pd is divided between the components in the circuit, as they are in series with each other

What can a potential divider be used for?

1. To supply a pd which is fixed at any value between 0 and the source pd

2. To supply a variable pd

3. To supply a pd that varies with a physical condition such as temperature or pressure

What is the total resistance of a potential divider with two resistors R₁ and R₂ in series?

R₁ + R₂

What is the current through a potential divider connected to a source of pd V₀?

I = V₀ / (R₁ + R₂)

What is the pd across R₁ in a potential divider?

V₁ = (V₀ × R₁) / (R₁ + R₂)

What is the pd across R₂ in a potential divider?

V₂ = (V₀ × R₂) / (R₁ + R₂)

How does a variable potential divider work?

A source pd is connected across a fixed length of uniform resistance wire, a sliding contact moves along the wire, giving a variable pd between the contact and one end of the wire

What can be used instead of resistance wire in a variable potential divider

A uniform track of suitable material, may be circular or linear

Give 2 examples of uses of variable potential dividers

Audio volume control, vary brightness of a bulb

What is the key advantage of using a potential divider over a variable resistor in series to control brightness?

A potential divider can reduce the current to zero, whereas a variable resistor in series can only reduce the current to a minimum determined by its maximum resistance, it cannot reach zero

What is a sensor circuit

A circuit that produces an output pd which changes as a result of a change of a physical variable such as temperature or light intensity

What does a temperature sensor consist of?

A thermistor and a variable resistor

How is the pd of a thermistor in a temperature sensor set?

By adjusting the variable resistor. With the thermistor temperature constant, the source pd is divided between the two components and the variable resistor sets the desired pd across the thermistor

What happens to the pd across a thermistor in a temperature sensor when temperature increases?

The thermistors resistance decreases, so it takes a smaller share of the source pd