Basic Knowledge of Electricity

: Current Divider Rule: Formula, Derivation, and Examples
2026/10/16
When resistors are connected in parallel, how much current flows through each resistor? The rule that lets us calculate these currents from the ratio of the resistance values is the current divider rule. This article explains the current divider rule with diagrams, covering the following topics. What the current divider rule is Current divider formulas, their derivation, and worked examples The difference between the current divider rule and the voltage divider rule What Is the Current Divider Rule?] The current divider rule is used to calculate the current through each resistor in a parallel circuit. The diagram above shows resistors ...

: Voltage Divider Rule: Formula, Derivation, and Examples
2026/10/16
When resistors are connected in series, how many volts appear across each resistor? The rule that lets us calculate these voltages from the ratio of the resistance values is the voltage divider rule. This article explains the voltage divider rule with diagrams, covering the following topics. What the voltage divider rule is Voltage divider formulas, their derivation, and worked examples The difference between the voltage divider rule and the current divider formula What Is the Voltage Divider Rule? The voltage divider rule is a rule for calculating the voltage across each resistor when resistors are connected in series. The diagram ...

: What Is Battery Internal Resistance?
2026/10/15
When you connect a device to a battery, the battery voltage may drop. A key concept for understanding this behavior is the battery’s internal resistance. This article explains the following aspects of battery internal resistance using diagrams: The meaning of battery internal resistance \(r\) and its equivalent circuit The difference between electromotive force and terminal voltage, and the equation relating them How to read the terminal voltage–current graph Current and terminal voltage under open-circuit and short-circuit conditions What Is Battery Internal Resistance? A battery has a very small resistance \(r\) inside it. This resistance \(r\) is called internal resistance. As ...

: Electric Potential vs. Voltage: Differences
2026/10/29
When studying electric circuits, you will come across the terms “electric potential” and “voltage.” Since both use the same unit, you may find it difficult to understand how they differ. Electric potential is the electrical “height” relative to a reference point, while voltage is the difference in electric potential between two points. This article uses diagrams to explain electric potential and voltage, covering the following topics: The meanings of electric potential and voltage, and how they differ Calculations for a circuit with dry cells connected in series Understanding electric potential and voltage through elevation and elevation difference How changing the ...

: Open Circuit vs. Short Circuit: Differences
2026/10/9
When studying electrical circuits, you will come across the terms "open circuit" and "short circuit. These terms are commonly used, but if you are just starting to learn about electrical circuits, their meanings may not be clear. This article uses diagrams and equations to explain the following aspects of open and short circuits: What open and short circuits mean and how they differ How current and voltage change when a circuit is opened or shorted The relationship between an OFF switch and an open circuit A short-circuit current calculation example and precautions The Difference Between Open and Short Circuits First, ...

: Voltage Source vs. Current Source: Differences
2026/10/7
When studying electric circuits, you may come across the terms “voltage source” and “current source.” The key to understanding the difference is whether the source maintains a constant voltage or a constant current as the load changes. This article explains the following topics using diagrams and equations. Differences between voltage sources and current sources Conditions for voltage sources and current sources to be equivalent Source transformation methods and calculation examples Differences Between Voltage Sources and Current Sources The diagram below compares voltage source and current source models that include internal resistance. A voltage source supplies voltage to a load. Its ...

: What Is a Current Source? Characteristics, Symbols, and Internal Resistance
2026/10/9
When studying electric circuits, you may come across the term “current source.” A current source supplies current to a circuit. However, ideal and practical current sources differ in how their output current behaves when a load is connected. For example, an ideal current source maintains a constant output current even when the load resistance \(R\) changes. In contrast, when a practical current source is modeled using an equivalent circuit with internal resistance, its output current decreases as the load resistance increases. This article explains the following topics about current sources: What Is a Current Source? Load Current When the Current ...

: What Is a Voltage Source? Characteristics, Symbols, and Internal Resistance
2026/10/9
When studying electric circuits, you may come across the term voltage source. A voltage source supplies voltage to a circuit. However, ideal and real voltage sources behave differently when a load is connected. For example, an ideal voltage source maintains a constant output voltage even when the load resistance \(R\) changes. A real voltage source has internal resistance, so its output voltage decreases as the load current increases. This article uses diagrams to explain the following topics: What a voltage source is Voltage across the load when the source’s internal resistance \(r\) is zero Voltage across the load when the ...

: RL Parallel Circuit (Admittance, Phasor Diagram)
2022/11/13
Regarding the RL parallel circuit, this article will explain the information below. Equation, magnitude, vector diagram, and admittance phase angle of RL parallel circuit admittance Admittance of the RL parallel circuit An RL parallel circuit is an electrical circuit consisting of a resistor \(R\) and an inductor \(L\) connected in parallel, driven by a voltage source or current source. The impedance \({\dot{Z}}_R\) of the resistor \(R\) and the impedance \({\dot{Z}}_L\) of the inductor \(L\) can be expressed by the following equations: \begin{eqnarray}{\dot{Z}_R}&=&R\tag{1}\\\\{\dot{Z}_L}&=&jX_L=j{\omega}L\tag{2}\end{eqnarray} , where \({\omega}\) is the angular frequency, which is equal to \(2{\pi}f\), and \(X_L\left(={\omega}L\right)\) is called inductive reactance, ...

: RC Parallel Circuit (Admittance, Phasor Diagram)
2022/11/13
Regarding the RC parallel circuit, this article will explain the information below. Equation, magnitude, vector diagram, and admittance phase angle of RC parallel circuit admittance Admittance of the RC parallel circuit An RC parallel circuit is an electrical circuit consisting of a resistor \(R\) and a capacitor \(C\) connected in parallel, driven by a voltage source or current source. The impedance \({\dot{Z}}_R\) of the resistor \(R\) and the impedance \({\dot{Z}}_C\) of the capacitor \(C\) can be expressed by the following equations: \begin{eqnarray}{\dot{Z}_R}&=&R\tag{1}\\\\{\dot{Z}_C}&=&-jX_C=-j\frac{1}{{\omega}C}=\frac{1}{j{\omega}C}\tag{2}\end{eqnarray} , where \({\omega}\) is the angular frequency, which is equal to \(2{\pi}f\), and \(X_C\left(=\displaystyle\frac{1}{{\omega}C}\right)\) is called capacitive reactance, ...