Potential Dividers - A-Level Physics OCR

Introduction to Potential Dividers

• A potential divider is a simple electrical circuit used to derive a fraction of the source voltage.
• It consists of resistors arranged in series across a voltage source.
• The voltage across each resistor is proportional to its resistance.

Diagram of a Potential Divider

• The circuit includes:
  • Resistors R1 and R2
  • Source voltage Vs
  • Output voltage Vout
• Formula: [ V_{out} = \frac{R_2}{R_1 + R_2} \times V_s ]_

Key Terms

• Vout: Output voltage (V)
• R1: Resistance of resistor 1 (Ω)
• R2: Resistance of resistor 2 (Ω)
• Vs: Source voltage (V)

Calculation Steps

1. Formula
   • [ V_{out} = \frac{R_2}{R_1 + R_2} \times V_s ]
2. Converting Units
   • To convert from kΩ to Ω, multiply by 1,000.
   • Example: 3.9 kΩ = 3,900 Ω.
3. Example Calculation
   • Given: R1 = 560 Ω, R2 = 3,900 Ω (3.9 kΩ), Vs = 12 V.
   • Substitute into formula: [ V_{out} = \frac{3,900}{560 + 3,900} \times 12 = 10.49 V ]
   • Thus, the output voltage Vout is 10.49 V.

Summary

• The output voltage in a potential divider circuit is always a fraction of the input voltage, determined by the relative resistances of the resistors in the circuit.
• Proper unit conversion and substitution into the potential divider formula are crucial for accurate calculation of Vout.