coulombs = amperes × seconds (1) solving (1) for the current, amperes = coulombs/seconds (2) substituting the given values in (2), amperes= (1/10) / (1/20000) = 2000 =Power.=--The term power means _the rate at which work is done;_ it is usually expressed as _the number of foot pounds done in one minute_, that is power = (foot pounds) / minutes _Power exerted for a certain time produces work._ =Ques. What is the mechanical unit of power?= Ans. The horse power. =Ques. What is one horse power?= Ans. 33,000 foot pounds per minute. The unit is due to James Watt as being the power of a strong London draught horse to do work during a short interval and used by him to measure the power of his steam engines. One horse power = 33,000 ft. lbs. per minute = 550 ft. lbs. per sec. = 1,980,000 ft. lbs. per hour. =Ques. What is one horse power hour?= Ans. Work done at the rate of one horse power for one hour. =Ques. What is the electrical unit of power?= Ans. The watt. =Ques. What is a watt?= Ans. It is the power due to a current of one ampere flowing at a pressure of one volt. One watt = one ampere × one volt. It is equal to one joule per second. =Ques. What is a kilowatt?= Ans. 1,000 watts. =The Watt-Hour.=--The elements which may be measured are, however, not only the volume of current, the unit of which is the ampere, and time, the unit of which is the hour, but also the _pressure_, the unit of which is the volt. It is evident that a perfect system of electrical measurement should take account of the total amount of energy consumed, and should depend not only upon the volume of current, but _also upon the pressure_ at which the current is applied. The basis of such a system if provided in a unit which is the product of the two units of current and pressure, and which is termed a _volt-ampere_ or _watt_. _The watt-hour represents the amount of work done by an electric current of one ampere strength flowing for one hour under a pressure of one volt._ EXAMPLE--An incandescent lamp taking one-half an ampere of current on a circuit having a pressure of 100 volts, or a lamp taking one ampere on a circuit having a pressure of 50 volts, would each be consuming 50 watts of energy, and this multiplied by the number of hours would give the total number of watt-hours for any definite time. _The watt, then, is an accurate and complete unit of measurement and is generally applicable to all forms of electrical consumption._