## Electric Current: The Most Basic Explanation From a Physics Point of View

In this lesson you will learn the basics of the electric current, i.e. the definition, its physical meaning and unit.

Electromagnetic phenomena and their applications

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Lesson ## Electric Current: The Most Basic Explanation From a Physics Point of View

In this lesson you will learn the basics of the electric current, i.e. the definition, its physical meaning and unit.

## Related formulas

Formula ## Electric current (definition)

`$$ I ~=~ \frac{Q}{t} $$`## Related Illustrations

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Lesson ## Voltage: How it is created by charge separation!

Here you will learn what voltage is, how it is generated by charge separation, how a voltage source can be created, and what voltage has to do with current.

## Related formulas

Formula ## Electrical Energy (Work, Voltage, Charge)

`$$ W ~=~ q \, U $$`## Related Illustrations

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Lesson ## Ohm's law: Formula, Graph and 3 Easy Examples

Here you learn Ohm's law, how it is expressed as a formula and as a graph. We also look at three examples.

## Questions & Answers

## Related formulas

Formula ## Ohm's Law (Resistance, Voltage, Current)

`$$ U ~=~ R \, I $$`## Related Illustrations

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Lesson ## Simple (Series and Parallel) Circuits. The Basics.

Here you will learn how an electrical circuit works and how to apply Ohm's Law to it. You will also learn about parallel and series circuits and their difference.

## Questions & Answers

## Related formulas

Formula ## Series circuit (total resistance, equivalent resistance)

`$$ R ~=~ R_1 ~+~ R_2 ~+~ R_3 ~+~ ... $$`Formula ## Series Circuit of Resistors (Total Current)

`$$ \class{red}{I} ~=~ \class{red}{I_1} ~=~ \class{red}{I_2} ~=~ \class{red}{I_3} ~=~ ... ~=~ \class{red}{I_n} $$`Formula ## Series Circuit of Resistors (Voltage)

`$$ U ~=~ U_1 ~+~ U_2 ~+~ U_3 ~+~ ... ~+~ U_n $$`Formula ## Parallel connection (total resistance, equivalent resistance)

`$$ \frac{1}{R} ~=~ \frac{1}{R_1} ~+~ \frac{1}{R_2} ~+~ \frac{1}{R_3} ~+~ ... $$`Formula ## Parallel Circuit of Resistors (Total Current)

`$$ \class{red}{I} ~=~ \class{red}{I_1} ~+~ \class{red}{I_2} ~+~ \class{red}{I_3} ~+~ ... ~+~ \class{red}{I_n} $$`Formula ## Parallel Circuit of Resistors (Total Voltage)

`$$ U ~=~ U_1 ~=~ U_2 ~=~ U_3 ~=~ ... $$`Formula ## Voltage Divider (Output and Input Voltage, Resistors)

`$$ U_{\text{out}} = \frac{R_2}{R_1 + R_2} \, U_{\text{in}} $$`Formula ## Practical Voltage Source (Ideal Voltage, Internal Resistance)

`$$ U = \frac{\class{blue}{U_0}}{1 + \frac{R_{\text i}}{R}} $$`## Related Illustrations

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Derivation ## Electric Power

Simple derivation of the electric power P, which we express with voltage U and current I and then rewrite using the URI formula.

## Related formulas

Formula ## Electric power (voltage, current)

`$$ P ~=~ U \, I $$`Formula ## Electric Power (Current, Resistance)

`$$ P ~=~ R \, I^2 $$`Formula ## Electric Power (Voltage, Resistance)

`$$ P ~=~ \frac{U^2}{R} $$`Formula ## Ohm's Law (Resistance, Voltage, Current)

`$$ U ~=~ R \, I $$`Formula ## Electric current (definition)

`$$ I ~=~ \frac{Q}{t} $$`Formula ## Electrical Energy (Voltage, Current, Time)

`$$ W ~=~ U \, I \, t $$`## Related Illustrations

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Lesson ## Plate Capacitor: Voltage, Capacitance and Eletric Force

Here the plate capacitor is simply explained. With the help of the capacitor you will learn about the electric voltage, electric field and electric capacitance and how to calculate them for a plate capacitor.

## Exercises with solutions

Exercise with solution ## Create a Plate Capacitor with a Certain Capacitance

Exercise with solution ## Charge in a thundercloud

Exercise with solution ## Capacitor with and without dielectric in comparison

## Derivations & Experiments

Derivation ## Plate Capacitor: Potential, E-field, Charge and Capacitance

Here, the electrostatic potential, electric field and the capacitance of a plate capacitor are derived using Laplace's equation.

## Related formulas

Formula ## Plate Capacitor (Force, Voltage, Charge, Distance)

`$$ F ~=~ \class{red}{q} \, \frac{U}{d} $$`Formula ## Plate Capacitor (Capacitance)

`$$ C ~=~ \varepsilon_0 \, \varepsilon_{\text r} \, \frac{A}{d} $$`Formula ## Plate Capacitor (Energy, Electric Field)

`$$ W_{\text{e}} ~=~ \frac{1}{2} \, \varepsilon_0 \, \varepsilon_{\text r} \, V \, E^2 $$`Formula ## Plate Capacitor (Electric Field, Voltage, Distance)

`$$ E ~=~ \frac{U}{d} $$`Formula ## Capacitor (Energy, Capacitance, Charge)

`$$ W_{\text{e}} ~=~ \frac{1}{2} \, \frac{Q^2}{C} $$`Formula ## Capacitor (Energy, Voltage, Capacitance)

`$$ W_{\text e} ~=~ \frac{1}{2} \, C \, U^2 $$`Formula ## Plate capacitor (potential, voltage, distance)

`$$ \varphi_x = - \frac{U}{d} \, x ~+~ \varphi_1 $$`Formula ## Plate Capacitor (Attraction Force, Voltage)

`$$ F ~=~ \frac{\varepsilon_0 \, \varepsilon_{\text r} \, A}{2d^2}\, U^2 $$`Formula ## Plate Capacitor (Attraction Force, Charge)

`$$ F ~=~ \frac{Q^2}{2\varepsilon_0 \, \varepsilon_{\text r} A^2} $$`## Related Illustrations

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Lesson ## RC Circuit: Charging and Discharging a Capacitor

Here you will learn about the RC circuit. This is a resistor and capacitor connected in series. The capacitor can be charged and discharged via the resistor.

## Exercises with solutions

Exercise with solution ## Charge, Capacitance and Half-Life of a Capacitor When Discharging From 50V to 15V.

## Related formulas

Formula ## Charging Capacitor (Current, Capacitance, Resistance, Time)

`$$ I(t) ~=~ I_0 \, \mathrm{e}^{-\frac{t}{R\,C}} $$`Formula ## Charging Capacitor (Voltage, Capacitance, Resistance, Time)

`$$ U_{\text C}(t) ~=~ U_0 \, \left(1 - \mathrm{e}^{-\frac{t}{\class{brown}{R}\,C}}\right) $$`Formula ## Charging a Capacitor (Voltage at the Resistor)

`$$ U_{\text R}(t) ~=~ U_0 \, \mathrm{e}^{-\frac{t}{R\,C}} $$`Formula ## Discharging Capacitor (Voltage, Capacitance, Resistance, Time)

`$$ U_{\text C}(t) ~=~ U_0 \, \mathrm{e}^{-\frac{t}{R\,C} } $$`Formula ## Discharging Capacitor (Discharge Current, Capacitance, Resistance, Time)

`$$ I(t) ~=~ -I_0 \, \mathrm{e}^{-\frac{t}{R\,C}} $$`Formula ## RC Circuit (Half-Life)

`$$ t_{\text h} ~=~ R\,C \, \ln(2) $$`Formula ## RC Circuit (Time Constant)

`$$ \tau ~=~ R \, C $$`## Related Illustrations

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Lesson ## Capacitive reactance of a capacitor

Learn what capacitive reactance is and how to determine it for a capacitor in an AC circuit. We also make a simple example!

## Related formulas

Formula ## Capacitive Reactance (Capacitance, Frequency)

`$$ \class{purple}{X_{\text C}} ~=~ -\frac{1}{2\pi \, f \, \class{purple}{C}} $$`## Related Illustrations

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Lesson ## Inductive Reactance of a Coil

Learn what inductive reactance is and how to determine it for a coil in an AC circuit.

## Related formulas

Formula ## Inductive Reactance (Inductance, Frequency)

`$$ \class{brown}{X_{\text L}} ~=~ 2 \pi \, f \, \class{brown}{L} $$`## Related Illustrations

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Lesson ## Left / Right-Hand Rule: How to Determine Lorentz Force Direction

You learn how to use the hand rule to determine the direction of the Lorentz force and whether you have to use your right or left hand.

## Related Illustrations

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Lesson ## Lorentz Force: How to Determine its Direction and Understand Formula

Learn how Lorentz force (magnetic force) deflects a moving charge (electron) in the magnetic field and how you can determine the direction of the deflection.

## Exercises with solutions

Exercise with solution ## An Ion Orbiting Around The Equator in The Magnetic Field

## Derivations & Experiments

Derivation ## Lorentz Force on Current-Carrying Wires

Derivation of the formulas for the Lorentz force on a current-carrying wire in the magnetic field or Lorentz force between two current-carrying wires.

## Related formulas

Formula ## Lorentz Force (Magnetic field, Velocity)

`$$ \class{green}{F} ~=~ q \, \class{blue}{v} \, \class{violet}{B} $$`Formula ## Lorentz Force (Angle, Magnetic Field, Velocity)

`$$ \class{green}{F} ~=~ q \, \class{blue}{v} \, \class{violet}{B} \, \sin(\alpha) $$`Formula ## Circular Motion in a Magnetic Field (Radius, Velocity, Mass)

`$$ r ~=~ \frac{ \class{brown}{m} \, \class{blue}{v} }{ |q| \, \class{violet}{B} } $$`Formula ## Cyclotron Frequency (B-field, Charge, Mass)

`$$ f ~=~ \frac{|q| \, \class{violet}{B}}{2\pi \, \class{brown}{m}} $$`Formula ## Circular Motion in the Magnetic Field (Period, Charge, Mass)

`$$ T ~=~ 2 \, \pi \frac{ \class{brown}{m} }{ |q| \, \class{violet}{B} } $$`Formula ## Current-Carrying Wire in Magnetic Field (Force, Current, Length)

`$$ \class{green}{F} ~=~ \class{blue}{I} \, L \, \class{violet}{B} $$`Formula ## Two Current-Carrying Wires (Force, Current, Distance)

`$$ \class{green}{F} ~=~ \frac{\mu_0 \, L}{2 \pi} \, \frac{ \class{blue}{I_1} \, \class{blue}{I_2} }{r} $$`## Related Illustrations

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Lesson ## Teltron Tube Experiment and How to Get The Specific Charge of a Particle

Here you will learn how a teltron tube experiment is set up, how it visualizes electron motion, and how you can use it to find out specific charge.

## Related formulas

Formula ## Lorentz Force (Magnetic field, Velocity)

`$$ \class{green}{F} ~=~ q \, \class{blue}{v} \, \class{violet}{B} $$`Formula ## Circular motion (centripetal force, velocity, radius)

`$$ F_{ \text z} ~=~ \frac{\class{brown}{m} \, \class{blue}{v}^2}{ r } $$`Formula ## Specific Charge (Magnetic Field, Velocity, Radius)

`$$ \frac{q}{\class{brown}{m}} ~=~ \frac{ \class{red}{v} }{ r \, \class{violet}{B}} $$`Formula ## Specific Charge (Voltage, Magnetic Field, Radius)

`$$ \frac{q}{\class{brown}{m}} ~=~ \frac{2 \, U_{\text B}}{r^2 \, \class{violet}{B}^2} $$`## Related Illustrations

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## Related formulas

Formula ## Lorentz Force (Magnetic field, Velocity)

`$$ \class{green}{F} ~=~ q \, \class{blue}{v} \, \class{violet}{B} $$`Formula ## Charge in an Electric Field (Force, Charge)

`$$ F ~=~ \class{red}{q} \, E $$`## Related Illustrations

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Lesson ## Hall Effect: A Simple Explanation of How Hall Voltage is Induced

Explanation of what the Hall effect is, how exactly the Hall voltage is generated and how you can calculate it and the Hall constant.

## Derivations & Experiments

Derivation ## Hall Voltage due to the Hall Effect

Derivation of the Hall voltage (via Hall effect), which depends only on quantities that we can easily determine in an experiment.

## Related formulas

Formula ## Hall Effect (Voltage, Hall Coefficient, Current, B-Field)

`$$ U_{\text H} ~=~ A_{\text H} \, \frac{I \, \class{violet}{B}}{d} $$`Formula ## Hall Effect (Hall Voltage, Charge Carrier Density)

`$$ U_\text{H} ~=~ \frac{1}{n \, q} ~ \frac{I \, \class{violet}{B}}{d} $$`Formula ## Hall Effect (Voltage, Drift Velocity)

`$$ U_\text{H} ~=~ v \, \class{violet}{B} \, h $$`Formula ## Hall constant (Electron and Hole Mobilities, Charge Carrier Density)

`$$ A_{\text H} ~=~ \frac{ \class{red}{p} \,{\mu_{\text +}}^2 ~-~ \class{blue}{n} \, {\mu_{\text -}}^2}{e \, (\class{red}{p} \, \mu_{\text +} ~+~ \class{blue}{n} \, \mu_{\text -})^2} $$`## Related Illustrations

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Derivation ## Capacitance - Series and Parallel Connection of Capacitors

Derive the total capacitance (equivalent capacitance) of a parallel circuit and a series circuit of two capacitors in an AC circuit.

## Related formulas

Formula ## Series circuit of capacitors (capacitance)

`$$ \frac{1}{C} ~=~ \frac{1}{C_1} ~+~ \frac{1}{C_2} ~+~... ~+~ \frac{1}{C_n} $$`Formula ## Series Circuit of Capacitors (Voltage)

`$$ U ~=~ U_1 ~+~ U_2 ~+~ U_3 ~+~ ... ~+~ U_n $$`Formula ## Series Circuit of Capacitors (Charge)

`$$ \class{red}{Q} ~=~ \class{red}{Q_1} ~=~ \class{red}{Q_2} ~=~ \class{red}{Q_3} ~=~ ... ~=~ \class{red}{Q_n} $$`Formula ## Parallel connection (total capacitance / equivalent capacitance)

`$$ C ~=~ C_1 ~+~ C_2 ~+~ ...~+~ C_n $$`Formula ## Parallel Circuit of Capacitors (Charge)

`$$ \class{red}{Q} ~=~ \class{red}{Q_1} ~+~ \class{red}{Q_2} ~+~ \class{red}{Q_3} ~+~ ... ~+~ \class{red}{Q_n} $$`Formula ## Parallel Circuit of Capacitors (Voltage)

`$$ U ~=~ U_1 ~=~ U_2 ~=~ U_3 ~=~ ... ~=~ U_n $$`## Related Illustrations

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Derivation ## Total (Equivalent) Inductance of a Series and Parallel Circuit of Coils

Derivation of the total inductance (equivalent inductance) of a parallel circuit and series circuit of two coils using the Faraday's law of induction.

## Related formulas

Formula ## Series circuit of coils (inductance)

`$$ L ~=~ L_1 ~+~ L_2 ~+~ ... ~+~ L_n $$`Formula ## Parallel circuit of coils (inductance)

`$$ \frac{1}{L} ~=~ \frac{1}{L_1} ~+~ \frac{1}{L_2} ~+~ ... ~+~ \frac{1}{L_n} $$`## Related Illustrations