Potentiometers
Electrical Circuits - OCR A-Level Physics
Key Definition
potentiometer
A variable potential divider. A resistor with a sliding contact that allows V_out to be adjusted continuously from 0 V to the full source p.d..
A variable potential divider. A resistor with a sliding contact that allows V_out to be adjusted continuously from 0 V to the full source p.d..
- A potentiometerA potential dividerA circuit that uses two or more resistors in series to produce a fraction of the source voltageThe energyThe capacity to do work. Measured in joules (J). transferred per unit chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). between two points. Measured in volts (V). Informal term for potential difference. across one of the resistors. with a sliding contact that allows continuous variation of the output voltageThe energyThe capacity to do work. Measured in joules (J). transferred per unit chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). between two points. Measured in volts (V). Informal term for potential difference. from zero to the supply voltageThe energyThe capacity to do work. Measured in joules (J). transferred per unit chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C). between two points. Measured in volts (V). Informal term for potential difference.. is a resistor with three terminals.
- A sliding contact moves along the resistive track.
- V_out is taken between the slider and one end.
- Moving the slider changes the ratio R_1 : R_2 continuously.
- This allows V_out to range from 0 V to the full supply p.d..
- Volume controls and dimmer switches.
- Varying p.d. from zero to maximum when measuring I-V characteristics.
- A potentiometerA potential divider with a sliding contact that allows continuous variation of the output voltage from zero to the supply voltage. gives a wider range than a simple variable resistor in series.
PotentiometerA potential divider with a sliding contact that allows continuous variation of the output voltage from zero to the supply voltage. circuit symbol and schematic
Three-terminal resistor with sliding arrow contact. V_in across full length, V_out from slider to one end.
Common Mistake
MEDIUM
Wrong: Confusing a potentiometerA potential divider with a sliding contact that allows continuous variation of the output voltage from zero to the supply voltage. with a simple variable resistor (rheostat).
Right: A rheostat has two terminals and changes total R. A potentiometer has three terminals and divides V. They are different devices.
Right: A rheostat has two terminals and changes total R. A potentiometer has three terminals and divides V. They are different devices.
Examiner Tips and Tricks
- Potentiometers are OCR-specific content.
- AQA does not examine them.
- In OCR exams, you may be asked why a potentiometer is preferred over a variable resistor for I-V investigations.