Direct Current

Direct current (DC) is defined as a current that is constant due to a steady, unidirectional flow of electrical charge. The voltage (V or v), or the potential difference between two points is a measure of the work required to move a unit charge from one point to another. The volt is equal to an energy level of one joule per coulomb. The flow of the current through a conductor generates heat because of the internal resistance.

This is ex­pressed by:

W=Rl²t 

where, 

W=work performed

R = resistance (the coefficient of proportionally between W and Pt) I = current

t = time that the current flows

The electric flow in DC circuits can be supplied by an independent voltage source, by an independent current source, or by dependent voltage and current sources. An independent voltage source supplies the same level of voltage regardless of the amount of current drawn. An indepen­dent current source supplies the same level of current (amperes) regardless of the level of voltage. The source current quantity of a dependent source is determined by a voltage or current source at some other location in the electrical system under consideration.

Resistance (R) is the measure of the tendency of a material to impede the flow of electrical charges through it. Resistance is "low" in a good conductor and "high" in poor conductors (the latter known as insulators). The unit of resistance, the ohm, is defined as a drop of one volt per ampere. Conductance (G) is the reciprocal of resistance, and can be viewed as the ratio of current to voltage.

For resistances connected in series with each other, the resultant ef­fective resistance is the sum of the individual resistances. For resistances connected in parallel with each other, the resultant effective conductance is the sum of the individual conductances.

Questionnaire:

• What id Direct current? Explain.