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What is Electrical Power and Energy [Audio Physics for Beginners]

Audio Basis - educational articles

Electrical power is electrical energy per second. Read below how power, energy, voltage, current, resistance are linked.

Electrical power, electrical energy


Electrical energy and thermal energy


In an electrical devices the energy is converted to other types of energy: mechanical, light, other. Rest part (or most of part for many kinds of electronic devices) of the electrical energy is converted to thermal energy via resistance.


Electrical energy in many cases converted to thermal one

Electrical energy to thermal one


When we reviewed voltage we discuss that voltage is potential, that can cause movement of charged particles (electrons).

  • When charged particles under voltage, they have potential energy.
  • When no voltage, the particles have no electrical energy.
  • When the particles moves under voltage, they have kinetic energy (energy of movement).



Electrical energy and magnetic energy


Electric energy that moves across wire generate the magnetic energy.

But the electric energy will consumed, if closed wire loop, placed in the magnetic field. As example, metal ring is placed about this wire.


Electrical energy converted to magnetic energy

Electrical energy converted to magnetic energy


Current in the ring flow inside the metal ring and energy is consumed from the electric wire via magnetic field.

Consuming the electrical energy (and current respectively) in the electric wire is increased. More current - more energy is lost at the electric wire for heat.



Graphical presentation of electrical energy


Energy of audio signal is considered as square of signal shape.


Graphical presentation of electrical energy

Graphical presentation of electrical energy



Electrical power and energy formula


Power is called as P.

Energy is called as E.

Power is the energy per second.


P = E / t, where

t is time.


Power is calculated several ways:

P = U * I

P = U2 / R

P = I2 * R,


U is voltage,

I is current,

R is resistance.



Yuri Korzunov,

Audiophile Inventory's developer



To be continued...

< Read about electrical resistance



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