Controlling the flow of water has allowed civilizations to develop over the course of history. Similarly, electricity is a fluid whose flow can be controlled.
Inventors such as Thomas Edison developed ways to manipulate electricity to illuminate homes and also to produce and distribute electricity through wires and circuits.
The amount of light is determined by the amount of current measured in amps where 1 amp = 1 coulomb/second
Electric current I is the rate of flow of electric charge q, at any instant, the current is the same anywhere along the wire of the circuit. Electric charge is neither created nor destroyed along the way.
I = d/dt
Hans Christian Ørsted used a voltaic pile to deflect a magnetic needle with an electric current and discovered electromagnetism.
Through the use of a voltaic pile, Edison perfected the telegraph, a device where electric current causes a magnet to move in another location, thus enabling long distance communication.
In a telegraph, to prevent signal loss, if the voltage is increased in proportion to the distance.
Ohm's Law - to make a current flow through a conductor a voltage is needed. The current is always proportional to the voltage.
A constant of proportionality is called R or resistance.
V = IR is Ohm's Law
An element with resistance within a current is called a resistor.
Ohm's law does not hold true in all situations, however it is pratical in most.
The amount of electric current that flows through a resistor depends on the voltage drop across it, how wide, how long it is, and what it is made of.
The resistance of an electric resistor is proportional to its length, inversely proportional to its area and proportional to its resistivity to hinder the flow of electrons. This tendency to resist is something all materials have, but to varying degrees. Multiple resistors in a series are called resistor series and is analogous to lengthening the resistor.
Putting resistors side by side increases the area through which electrons can flow (known as resistors in parallel) and have a lower resistance than either one alone.
What resists the flow of electricity in a conductor? In a metal, electrons move constantly in different directions. The electrons orbit with the metal as if it were a molecule. This flow has no resistance and does not create a net flow in or out. If the conductor is in electrostatic equilibrium there is not electric field inside and no voltage difference. If a battery makes electric current flow, equilibrium is destroyed causing an electric field to form within the metal. Inside a perfect crystalline metal, the mobile electrons would continually accelerate. Impurities of crystals cause resistance by preventing acceleration of electrons.
As current flows through a resistor the energy that is turned into heat is equal to the amount of charge of flow multiplied by the change in potential. The rate of heating of power consumed is equal to IV. Using Ohm's law, power can be written as P = IV = I^2R or V^2/R
1 watt = 1 amp x a volt
Conservation of charge and of energy are derived from Ohm's law.
A capacitor in a circuit stores charge.
Time is equal to capacitance, or resistance for capacitor to empty.
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