voltage

Voltage

      Pictorially, if one joule of Energy (1 J) is required to move the one coulomb (1 C) of charge of Fig. 2.10 from position xto position y,the potential difference or voltage between the two points is one volt (1 V). If the energy required to move the 1 C of charge increases to 12 J due to additional opposing forces, then the potential difference will increase to 12 V. Voltage is therefore an indication of how much energy is involved in moving a charge between two points in an electrical system. Conversely, the higher the voltage rating of an energy source such as a battery, the more energy will be available to move charge through the system. Note in the above discussion that two points are always involved when talking about voltage or potential difference. In the future, therefore, it is very important to keep in mind that a potential difference or voltage is always measured between two points in the system. Changing either point may change the potential difference between the two points under investigation. Ingeneral,the potential difference between two points is determined by

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current

 Current

    If 6.242x 10^18 electrons drift at uniform velocity through the imaginary circular cross section  in 1 second,the flow of charge, or current,is said to be 1 ampere(A) in honor of André Marie Ampère . This is an enormous number of electrons passing through the surface in 1 second. The Current associated with only a few electrons per second would be inconsequential and of little practical value. To establish numerical values that permit immediate comparisons between levels, a coulomb(C) of charge was defined as the total charge associated with  6.242x 10^18 electrons. The charge associated with one Electron can then be determined from