What is a potential divider?

A circuit that uses two or more resistors in series to produce an output voltage that is a fraction of the input voltage.

State the potential divider equation for finding the output voltage across R₂ when two resistors R₁ and R₂ are connected in series.

Vout = Vin × R₂/(R₁ + R₂)

In the potential divider equation Vout = Vin × R₂/(R₁ + R₂), what does Vin represent?

The input voltage (the total voltage supplied across both resistors in series).

Calculate the output voltage when input voltage = 18 V, resistor 1 = 3400 Ω, resistor 2 = 3700 Ω.

Output voltage = 18 × 3700 ÷ (3400 + 3700) = 9.38 V.

Why is the current through each resistor in a series potential divider circuit identical?

Because resistors in series carry the same current, as there is only one path for current to flow.

How does V = IR apply to each resistor in a potential divider circuit?

The voltage across each resistor equals the common current multiplied by that resistor's resistance, so each resistor has a voltage proportional to its resistance.

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Electricity

Potential divider

4 things to know
Papers 1 and 3

Overview

The potential divider equation, and using an LDR or thermistor to make a sensing circuit.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Numbers

What is the potential divider equation, and why is the current the same through each resistor?

Numbers

What does the potential divider equation assume, and what do the resistor values affect?

Process

How do an LDR and a thermistor behave in a potential divider?

Key term

How can a potential divider be made to supply a variable potential difference?

Questions from this subtopic

Each one with the model answer underneath.

1
What is a potential divider?
Model answer
A circuit that uses two or more resistors in series to produce an output voltage that is a fraction of the input voltage.
2
State the potential divider equation for finding the output voltage across R₂ when two resistors R₁ and R₂ are connected in series.
Model answer
Vout = Vin × R₂/(R₁ + R₂)
3
In the potential divider equation Vout = Vin × R₂/(R₁ + R₂), what does Vin represent?
Model answer
The input voltage (the total voltage supplied across both resistors in series).
4
Calculate the output voltage when input voltage = 18 V, resistor 1 = 3400 Ω, resistor 2 = 3700 Ω.
Model answer
Output voltage = 18 × 3700 ÷ (3400 + 3700) = 9.38 V.
5
Why is the current through each resistor in a series potential divider circuit identical?
Model answer
Because resistors in series carry the same current, as there is only one path for current to flow.
6
How does V = IR apply to each resistor in a potential divider circuit?
Model answer
The voltage across each resistor equals the common current multiplied by that resistor's resistance, so each resistor has a voltage proportional to its resistance.

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