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The hyperphysics guide to DC electrical circuits
Submitted by reikiman on Thu, 04/17/2008 - 07:57
Resistence: "The electrical resistance of a circuit component or device is defined as the ratio of the voltage applied to the electric current whichflows through it"
Electric Current: "Electric current is the rate of charge flow past a given point in an electric circuit, measured in Coulombs/second which is named Amperes."
Voltage: "Voltage is electric potential energy per unit charge, measured in joules per coulomb ( = volts). It is often referred to as "electric potential", which then must be distinguished from electric potential energy by noting that the "potential" is a "per-unit-charge" quantity."
Electric Field: "Electric field is defined as the electric force per unit charge. The direction of the field is taken to be the direction of the force it would exert on a positive test charge. The electric field is radially outward from a positive charge and radially in toward a negative point charge."
Batteries: "Batteries use a chemical reaction to do work on charge and produce a voltage between their output terminals. The basic element is called an electrochemical cell and makes use of an oxidation/reduction reaction. An electrochemical cell which produces an external current is called a voltaic cell. Voltages generated by such cells have historically been referred to as emf (electromotive force). "
Moving Coil Meters: "The design of a voltmeter, ammeter or ohmmeter begins with a current-sensitive element. Though most modern meters have solid state digital readouts, the physics is more readily demonstrated with a moving coil current detector called a galvanometer. "
Electromotive Force: "When a voltage is generated by a battery, or by the magnetic force according to Faraday's Law, this generated voltage has been traditionally called an "electromotive force" or emf. The emf represents energy per unit charge (voltage) which has been made available by the generating mechanism and is not a "force". The term emf is retained for historical reasons. It is useful to distinguish voltages which are generated from the voltage changes which occur in a circuit as a result of energy dissipation, e.g., in a resistor. "