Electric Circuits: Resistors and Potential Dividers

Vocabulary flashcards covering linear and non-linear resistors, fixed and variable resistors, rheostats, potentiometers, and potential divider circuit operation and formulas.

Resistor Tolerance (No Fourth Band)

The default tolerance assigned to a resistor when no fourth color band is present, which is $20\%$.

Linear Resistors

Resistors whose current is precisely proportional to the applied voltage (obeying Ohm's Law) and whose resistance changes as a function of applied voltage and temperature.

Fixed Resistors

Resistors possessing a single fixed resistance value, commonly manufactured from carbon, that can handle high voltages but are less stable due to a high temperature coefficient.

Variable Resistors

Resistors designed to allow their resistance value to be adjusted, typically by using a mechanical movement such as a sliding contact to vary the length of the wire.

Variable Resistors (Rheostat and Potentiometer)

Mechanical wire-wound components used either as a rheostat to control current or as a potentiometer to divide voltage.

Rheostat

A variable resistor configured to regulate the current within an electrical circuit.

Potentiometer

A variable resistor configured as a variable voltage divider to obtain a variable potential difference from a fixed applied voltage.

Nickel and Chromium (Resistance Wire)

The metals commonly chosen as wire materials in wire-wound variable resistors due to their low temperature coefficient of resistance.

Potential Divider

A circuit that produces an output voltage ($V_{\text{out}}$) that is a fraction of its input voltage ($V_{\text{in}}$), thereby dividing an applied voltage into two or more smaller voltages.

Potential Divider Circuit Diagram

A circuit where a fixed voltage $V$ is applied across a wire-wound resistor of total resistance $R$, and a sliding contact $C$ taps off an adjustable potential difference $V_2$.

Potential Divider Formula

The mathematical formula giving output voltage as a fraction of input voltage: $V_{\text{out}} = \frac{R_2}{R_1 + R_2} V_{\text{in}}$.

Potential Divider Equal Resistance Case

The special condition where $R_1 = R_2 = r$, resulting in $V_{\text{out}} = \frac{1}{2} V_{\text{in}}$, which splits the input voltage into two equal halves at the output.

Applications of Potential Dividers

Practical uses including adjusting voltage levels, measuring voltage accurately, serving as the volume control knob in music systems, and operating in sensor circuits alongside thermistors or light-dependent resistors.

Non-Linear Resistors

Resistors whose resistance values fluctuate in response to temperature or voltage changes, subdivided into thermistors, varistors, and photo resistors.

Thermistor

A type of non-linear resistor whose resistance varies significantly with changes in temperature.