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

Audio Basis - articles about audio

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

updated

Author: Yuri Korzunov,
Audiophile Inventory's developer with 25+ year experience in digital signal processing,
author of the articles that make audio easy for beginners

Electrical energy and thermal energy

In electrical devices, the energy is converted to other types of energy: mechanical, light, others. The rest of the electrical energy is converted to thermal energy via resistance. Practically, a significant part of the electrical energy is wasted on heat.

Electrical energy in many cases is converted to the thermal one

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

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

Electrical energy and magnetic energy

The electric energy, that moves through a wire (conductor), generates magnetic energy.

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

Electrical energy converted to magnetic energy

The current in the ring flow inside the metal ring and energy is consumed from the electric wire via the 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

The energy of the audio signal is considered as a square of signal shape.

Graphical presentation of electrical energy

Electrical power and energy formula

Power is called P.

Energy is called E.

Power is the energy per second.

P = E / t, where

t is time.

Power is calculated in several ways:

P = U * I

P = U2 / R

P = I2 * R,

where

U is voltage,

I is current,

R is resistance.

Electrical power types

DIN

DIN POWER is a value of sine power:

• on frequency 1000 Hz
• during 10 minutes and
• non-linear distortions (THD) at audio unit output lesser 1%.

RMS

RMS (Rated Maximum Sinusoidal) is maximal sine audio power when audio unit is capable to work:

• on frequency 1000 Hz and
• during 1 hour and
• without damage.

PMPO

PMPO (Peak Music Power Output) is maximum sine audio power when an audio unit is capable to work:

• on frequency lesser than 250 Hz (as rule, 100 Hz) and
• during 1 second and
• without damage.

DIN POWER  <  RMS  <  PMPO

How to convert PMPO to RMS power?

There is no universal method to convert PMPO to RMS safely.

Theoretically, if you know exactly PMPO's measurement conditions for a given device, you can calculate PMPO energy and calculate the power with the same energy but during 1 hour. It will be like RMS.

But, for calculated RMS, the cooling abilities of the device and its resistance to the temperature may cause damage issues. And actual RMS should be lesser or, maybe, higher.

Audiophile Inventory's developer

What is the unit of electric energy?

Electrical enegry is measured in Joule or Watt × second/Watt × hour.