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Leakage describes an unwanted loss, or leak, of something which escapes from its proper location. In everyday usage, leakage is the gradual escape of matter through a leak-hole. In different fields, the term may have specialized meanings.

Chemistry

In chemistry, leakage is a process in which material is lost, intentionally or accidentally, gradually through the holes or defects of their containers. The material lost is usually fluid, usually liquid or powder and sometimes gas, from an imperfectly sealed container. Often, leakage can be disastrous if the leaked material is harmful or corrosive.

A zinc-carbon battery is an example of an easy-leaking system. The electrolytes inside the cell sometimes leak out of the cell shell, and cause damage to an electronic appliance.

Economics

In economics, leakage is the non-consumption uses of income, including saving, taxes, and imports. In the Keynesian injection-leakage or circular flow model, leakages are combined with injections to identify equilibrium aggregate output. The model is best viewed as a circular flow between national income, output, consumption, and factor payments. Savings, taxes, and imports are "leaked" out of the main flow, reducing the money available in the rest of the economy.

The simple model of credit creation assumes all loans borrowed from banks in a fractional-reserve banking system are re-deposited to the system. This allows simple calculation of amount of credit created. Therefore, in credit creation, cash leakage refers to the sums of money borrowed from banks but were not re-deposited. Cash leakage, in this case, lowers the ability of credit creation.

Electronics

In electronics, leakage may mean a gradual loss of energy from a charged capacitor. It is caused by undesired imperfection of some dielectric materials used in capacitors, also known as dielectric leakage. It is a result of the dielectric material not being a perfect insulator and therefore allowing a leakage current to flow, slowly discharging the capacitor.

Leakage may also mean an unwanted transfer of energy from one circuit to another. For example, magnetic lines of flux will not be entirely confined within the core of a power transformer; another circuit may couple to the transformer and receive some leaked energy at the frequency of the electric mains, which will cause audible hum in an audio application.

It is fatal in case leakage occurs in a high-voltage system and humans are in contact with the leak, especially when a person accidentally grounds a high-voltage power line.

Retail

Retail leakage occurs when members of a community spend money outside that community or when money spent inside that community is transferred outside the community. For example, crossing a border to buy goods forgoes the same purchase that could have been made inside the community. Many chain stores have high leakages rates due to the transferring of sales revenue to a corporate headquarters.

In addition, in retail trade, leakage, or shrinkage can also mean the loss of stock without payment, typically due to theft by employees or shoplifters.

Sound recording

In sound recording, leakage (also called spillage) occurs when audio intended for one track is picked up inadvertently by another track's microphone in a multitrack recording.

Multitrack recording is at its optimum when there is sufficient isolation between individual tracks to allow freedom in remixing each track to a desired sound level. Reasonable isolation can be achieved (even in a live recording) by careful microphone placement, or by the separation of sound sources. Sound leakage can limit or even ruin the remixing and overdubbing potentials of a multitrack recording, when one sound interferes with another sound on a track.

Other fields

Leakage may also have the following meanings in other fields:

• In medicine, anal leakage is a condition of faecal incontinence.
• In quantum mechanics, semiconductor leakage is a quantum phenomenon involving unwanted Quantum tunnelling through an insulating region.
• In tourism, leakage refers to the loss of tourist revenue from a country. (See leakage effect).

References

1. WordNet
2. E. Cheng et al, Chemistry - A Modern View 2, Aristo-Wilson, Hong Kong, 2004
3. EconPlace
4. Ngai, J. et al, Economics and You 5, Manhattan, Hong Kong, 2005.
5. Associated Research Tech Info
6. Glossary from Electric Fence
7. Glossary from System Connection

• Articles lacking sources from December 2006
• Electronics
• Chemical processes
• Distribution, retailing, and wholesaling
• Sound recording
• Manufacturing