United States dollar

The United States dollar (sign: $; code: USD; also abbreviated US$ and referred to as the dollar, U.S. dollar, or American dollar) is the official currency of the United States and its overseas territories. It is a Federal Reserve Note and consists of 100 smaller cent units.

The U.S. dollar is fiat money. It is the currency most used in international transactions and is the world's most dominant reserve currency. Several countries use it as their official currency, and in many others it is the de facto currency. Besides the United States, it is also used as the sole currency in two British Overseas Territories in the Caribbean: the British Virgin Islands and the Turks and Caicos islands. A few countries use only the U.S. Dollar for paper money, while the country mints its own coins, or also accepts U.S. coins that can be used as payment in U.S. dollars, such as the Susan B. Anthony dollar.

Overview

The Constitution of the United States of America provides that the United States Congress has the power "To coin money". Laws implementing this power are currently codified at 31 U.S.C. § 5112. Section 5112 prescribes the forms, in which the United States dollars should be issued. These coins are both designated in Section 5112 as "legal tender" in payment of debts. The Sacagawea dollar is one example of the copper alloy dollar. The pure silver dollar is known as the American Silver Eagle. Section 5112 also provides for the minting and issuance of other coins, which have values ranging from one cent to 50 dollars. These other coins are more fully described in Coins of the United States dollar.

United States one hundred-dollar bill

The United States one hundred-dollar bill ($100) is a denomination of United States currency featuring statesman, inventor, diplomat and American founding father Benjamin Franklin on the obverse of the bill. On the reverse of the banknote is an image of Independence Hall. The $100 bill is the largest denomination that has been printed since July 13, 1969, when the denominations of $500, $1,000, $5,000, and $10,000 were retired. The Bureau of Engraving and Printing says the average life of a $100 bill in circulation is 90 months (7.5 years) before it is replaced due to wear and tear.

The bills are also commonly referred to as "Bens", "Benjamins" or "Franklins", in reference to the use of Benjamin Franklin's portrait on the denomination, or as "C-Notes", based on the Roman numeral for 100. The bill is one of two denominations printed today that does not feature a President of the United States; the other is the $10 bill, featuring Alexander Hamilton. It is also the only denomination today to feature a building not located in Washington, D.C., that being the Independence Hall located in Philadelphia on the reverse. The time on the clock of Independence Hall on the reverse, according to the U.S. Bureau of Engraving and Printing, shows approximately 4:10 on the older contemporary notes and 10:30 on the series 2009A notes released in 2013.

Ultrasonic motor

An ultrasonic motor is a type of electric motor powered by the ultrasonic vibration of a component, the stator, placed against another component, the rotor or slider depending on the scheme of operation (rotation or linear translation). Ultrasonic motors differ from piezoelectric actuators in several ways, though both typically use some form of piezoelectric material, most often lead zirconate titanate and occasionally lithium niobate or other single-crystal materials. The most obvious difference is the use of resonance to amplify the vibration of the stator in contact with the rotor in ultrasonic motors. Ultrasonic motors also offer arbitrarily large rotation or sliding distances, while piezoelectric actuators are limited by the static strain that may be induced in the piezoelectric element.

One common application of ultrasonic motors is in camera lenses where they are used to move lens elements as part of the auto-focus system. Ultrasonic motors replace the noisier and often slower micro-motor in this application.