Resistor Circuit Formulas |
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\(R \;=\; \dfrac{ V }{ I }\) (Resistor) \(V \;=\; R \cdot I \) \(I \;=\; \dfrac{ V }{ R } \) |
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| \(R_t \;=\; R_1 + R_2 + R_3 \; + ... + \; R_n \) (Series Circuit) | ||
| \( \dfrac{1}{R_t} \;=\; \dfrac{1}{R_1} + \dfrac{1}{R_2} + \dfrac{1}{R_3} \; + ... +\; \dfrac{1}{R_n} \) (Parallel Circuit) | ||
| Symbol | English | Metric |
| \(R\) = Resistance | \(\Omega\) | \(kg-m^2\;/\;s^3-A^2\) |
| \(V\) = Voltage | \(V\) | \(kg-m^2 \;/\; s^3-A\) |
| \( I \) = Current | \(I\) | \(C \;/\; s\) |
Resistor is a passive two terminal electrical component that limits the flow of electric current. It's designed to have a specific resistance value, measured in ohms. Resistors are widely used in electronic circuits for various purposes, such as voltage division, current limiting, signal conditioning, and impedance matching. Physically, resistors can come in various shapes and sizes, but the most common type is a small cylindrical component with two leads protruding from either end. Resistors can be made from different materials, such as carbon composition, metal film, or metal oxide, which affect their performance characteristics such as tolerance, temperature coefficient, and power handling capability.
Resistors are characterized by their electric resistance value, tolerance, power rating, and temperature coefficient. Resistance value determines how much the resistor impedes the flow of current, tolerance specifies the allowed deviation from the nominal resistance value, power rating indicates how much power the resistor can dissipate without damage, and temperature coefficient describes how the resistance changes with temperature.
How Resistors Work
Resistive Material - Resistors are typically made of materials that resist the flow of electric current. These materials have high resistivity, meaning they impede the flow of electrons.
Ohm's Law - According to Ohm's law, the voltage across a resistor is directly proportional to the current passing through it and inversely proportional to its resistance.
Limiting Current - When resistors are placed in a circuit, they restrict the flow of current. The amount of resistance determines how much current will flow through the resistor for a given voltage, as per Ohm's law.
Dissipating Energy - As current passes through the resistor, energy is dissipated in the form of heat due to the resistance of the material. This dissipation of energy is what limits the current flow through the circuit.
Stability - Resistors are designed to have stable resistance values over a range of operating conditions such as temperature and voltage. This stability ensures that they provide consistent performance in electronic circuits.
Types of Resistors - There are various types of resistors, including carbon composition resistors, metal film resistors, wirewound resistors, and variable resistors (potentiometers). Each type has different characteristics and applications.
Color Coding - To indicate their resistance values, most resistors are color coded with bands painted around their bodies. By interpreting the colors according to a standardized code, you can determine the resistance value of the resistor.
Applications - Resistors are used in numerous applications in electronics and electrical circuits. Some common uses include voltage division, current limiting, voltage dropping, signal conditioning, and biasing components in transistors and integrated circuits.
