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# Direct Current (DC)

## Current Divider Rule in parallel resistors

Current divider in parallel resistors

By using the current divider rule, we can find the current in each resistor connected in parallel. The electric current passing through a circuit of two resistors in parallel is divided in two.

## Resistors in series and parallel (Equivalent resistor value)

Resistors in series and parallel

How to calculate resistors in series and resistors in parallel.
How to calculate resistors in parallel using conductance.
Formulas

## What is the Internal Resistance of a Voltage Source?

Internal resistance of a voltage source

Voltage sources, whether batteries, generators, etc., are not ideal (perfect). A real voltage source is composed of an ideal voltage source in series with a resistance called internal resistance.

## Ohm’s Law and the Electric Power – Formulas

Ohm’s Law and the Electric Power – Formulas

Ohm’s Law relates in one equation the voltage, the current and resistance. Resistance = Resistor’s value.
A more complete expression of Ohm’s Law is achieved using the electric power formula

## Wirewound Resistor (Wire wound Resistor)

What is a wirewound resistor?

A Wirewound resistor is a resistor made with a conductive wire of a high resistivity. This wire is made of a special alloy and it is wound on a support tube of refractory material such as ceramics, porcelain, etc.

## Ohm’s Law Tutorial – Ohm’s Law Triangle

Ohm’s Law explanation

Ohm’s law states that the voltage across a resistor is directly proportional to the current flowing through the resistance and directly proportional to the resistance of the circuit.

## Series/Parallel Resistor Reduction

Series/Parallel Resistor Reduction.

Resistors reduction can be done making some simplifications using resistors in series and resistors in parallel formulas.

## Mesh Current Method in a Resistor Network

Mesh Current Method in a Resistor Network

The Mesh current method is very useful to know all the current  in a network of only resistors. This method, a little more extended, is also applied to circuits where there are resistances and reactance.

## Millman’s Theorem – Millman’s equivalent circuit

What is a Millman’s Theorem?

Millman’s theorem is used to directly obtain the voltage between the ends of a parallel branch circuit. Equivalent Millman circuit Formulas, example.

## Window comparator using op amps

Window comparator using op amps

A window comparator using operational amplifiers lets you know if a signal (voltage level) is within or outside a previously defined acceptable voltage limit. Using a comparator or operational amplifier that controls the upper voltage level and another comparator that controls the lower voltage level, a window comparator can be implemented.

## Capacitor Charging Process (RC circuit)

Capacitor charging process

Capacitor charging process shows the variation of voltage and current in the capacitor over time, when it is connected to a DC voltage source

## Voltage – Electrical Potential Difference

What is a Voltage?

Potential difference or Voltage is a kind of force that push charges through a conductor. The larger the voltage, the larger the force

## Benjamin Franklin’s Fluid Theory

Benjamin Franklin’s Fluid Theory

Benjamin Franklin imagined the electricity as a invisible fluid. Franklin assured that if any body had more fluid than usual, it could have a positive charge, but if it had less fluid than normal it had negative charge.

## Voltage Divider Rule

What is a Voltage divider?

The Voltage divider is a circuit that allows us to obtain an output voltage less or equal to the input voltage. The output voltage is normally obtained across ground and the resistor connected to it, but it could be across any of the other resistors.

## What is Direct Current? – What is DC?

What is Direct Current? – DC

Direct Current (DC), is the result of the flow of electrons (negative charge) in a conductor (most of the time, wires of copper) that goes only in one direction.

## What is Electrical Resistivity? – Electrical Conductivity

What is Electrical Resistivity?

Electrical resistivity [ρ] (rho) is a characteristic of materials and has ohm-meter unit. Resistivity indicates how much the material opposes the flow of electric current.

## Capacitor and Direct Current (DC) – Dielectric

Capacitor and Direct Current

If a battery is connected to a capacitor, it will allows no direct current (DC) to flow through. If a not charged capacitor is connected across the terminals of a battery, a transient current flows as the capacitor plates charge up.

Capacitor and Direct Current. Current starts from its maximum value and decreases to 0 amps. This current is called “transient current”.

## Superposition Theorem – Example

The Superposition Theorem

The Superposition theorem states that the effect of two or more voltage sources in a resistor is equal to the sum of the individual effects of each source taken separately, replacing all the remaining voltage sources with short circuits.

## What is Electrical Resistance? Obtaining a material’s resistance

What is Electrical Resistance? Obtaining a material’s resistance

The electrical resistance is a measurement of the opposition that offers a material to the passage of electrons (the electric current). When a material, such as metals has many free electrons, it allows the easy flow of electrons and it is called conductor.

## First Right Hand Rule. Magnetic Force on a Current-Carrying Wire

First Right Hand Rule

The First Right Hand Rule or (Magnetic Force induced on a Current-Carrying Wire) says that if a current-carrying wire is in the presence of a magnetic field, a force is exerted on the wire.

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