Wednesday, September 8, 2010

Current Electricity and Electric Circuits

Physical Quantities and Measurements:

          Charge (Q) measured in coulombs (C)

          Current (I) measured in amperes (A)

          Time (t) measured in seconds

          Electrical Potential Difference (Voltage) measured in volts (V)

          Energy (E) measured in joule (J)

Facts Learned:

•  Current is the total amount of charge in Coulombs that goes through a point in a conductor, divided by the time it takes. Current is symbolized by I. The formula is:
 I (Current in Amperes) = Q (charge in Coulombs) divided by t (time in seconds) or I = Q / t

• The base unit for current is C/s which is named Ampere. It is represented by (A). One ampere = one Coulomb of charge moving through a point in the conductor / second.

• Conventional current flow vs. electron flow:
              - Conventional current flow is from positive to negative.
              - Electrons are negative and flow from negative to positive.

• Voltage vs. Current

              - Voltage is the electrical potential difference between two points.
              - Voltage would move from a point of higher potential to a point of lower if given the chance (until the levels equalize).
              - Current is the rate of flow of charge.

• In coloured writing convention used to keep track of electron current flow, black represents the negative terminal and red represents the positive terminal.

• In a direct current, the current flows in one direction. It flows from the power supply, through the conductor, to a load, and back to the power supply.

• In an alternating current the electrons reverse the direction of their flow periodically, with the help of electric and magnetic forces.

• Work is done by the power supply to increase the electrical potential energy of each coulomb of charge from a low to a high value. As the charge flows through a load, its energy decreases.
The electric potential energy (voltage) for each Coulomb of charge in a circuit is called the electric potential difference.

• The energy (needed to do work) = electric potential difference * charge or E = Q* V

• 1 Volt is  the electric potential difference between two points (if 1 joule of work is required to move 1 coulomb of charge between 2 points.


You can aslo check the Video on Electric Circuits

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