Browse Definitions :

ampere per meter squared (A/m 2)

The ampere per meter squared, symbolized A/m 2 , is the International Unit of electric current density . A current density of 1 A/m 2 represents one ampere of electric current flowing through a material with a cross-sectional area of one square meter.

The ampere per meter squared is a small unit of current density. Suppose a wire has a cross-sectional area of one millimeter squared (1 mm 2 ). This is 0.000001 meter squared (10 -6 m 2 ). If the current density in this wire is 1 A/m 2 , then the wire carries 10 -6 A, or one microampere (1 µA), a tiny current. Suppose this same wire carries a current of one ampere (1 A), which is an entirely plausible scenario. Then the current density in the wire is 1,000,000 amperes per meter squared (10 6 A/m 2 ).

Sometimes, larger units of current density are specified. For example, one ampere per millimeter squared (A/mm 2 ) represents a current of 1 A flowing through a conductor with a cross-sectional area of 1 mm. This unit is equal to 1,000,000 (10 6 ) A/m 2 . One milliampere per millimeter squared (mA/mm 2 ) represents a current of 1 mA flowing through a conductor with a cross-sectional area of 1 mm. This unit is equal to 1,000 (10 3 ) A/m 2 .

Determination of current density is straightforward in direct-current ( DC ) and low-frequency alternating-current ( AC ) circuits, because the current is distributed uniformly throughout the cross section of a solid conductor. But at radio frequencies ( RF ), more current flows near the outer surface of a solid conductor than near its center. This is known as skin effect , and it dramatically reduces the conductivity of wires in RF applications as compared with DC and low-frequency AC circuits. At RF, current density is sometimes near zero near the center of a solid conductor, and quite high near the outer periphery. The average current density can nevertheless be calculated according to the following formula:

D = I / X

where D is the current density in amperes per meter squared, I is the current in amperes, and X is the cross-sectional area of the conductor in meters squared.

Also see ampere , meter squared , skin effect , and International System of Units ( SI ).

This was last updated in February 2011
  • pure risk

    Pure risk refers to risks that are beyond human control and result in a loss or no loss with no possibility of financial gain.

  • risk reporting

    Risk reporting is a method of identifying risks tied to or potentially impacting an organization's business processes.

  • risk assessment

    Risk assessment is the identification of hazards that could negatively impact an organization's ability to conduct business.

  • encryption key

    In cryptography, an encryption key is a variable value that is applied using an algorithm to a string or block of unencrypted ...

  • payload (computing)

    In computing, a payload is the carrying capacity of a packet or other transmission data unit.

  • script kiddie

    Script kiddie is a derogative term that computer hackers coined to refer to immature, but often just as dangerous, exploiters of ...

  • What is risk mitigation?

    Risk mitigation is a strategy to prepare for and lessen the effects of threats faced by a business.

  • fault-tolerant

    Fault-tolerant technology is a capability of a computer system, electronic system or network to deliver uninterrupted service, ...

  • synchronous replication

    Synchronous replication is the process of copying data over a storage area network, local area network or wide area network so ...