Charge,Current,Voltage Charge

Charge,Current,Voltage

Charge

Charge is an electrical property of the atomic particles of which matter consists, measured in coulombs (C).

The following points should be noted about electric charge:

The coulomb is a large unit for charges. In 1 C of charge, there are (1/1.602×10^˗19 = 6.24×10¹⁸) electrons. Thus realistic or laboratory values of charges are on the order of pC, nC, or μC.

According to experimental observations, the only charges that occur in nature are integral multiples of the electronic charge е = ˗ 1.602×10^˗19

The law of conservation of chargestates that charge can neither be created nor destroyed, only transferred. Thus the algebraic sum of the electric charges in a system does not change.

Electric current

Electric current is the time rate of change of charge, measured in amperes (A).

Mathematically, the relationship between current i, charge q, and time t is

where current is measured in amperes (A), and (1 ampere = 1 coulomb/second )

There are two types of current

direct current(dc)

A direct current (dc) is a current that remains constant with time.

By convention the symbol I is used to represent such a constant current. Waveform of direct current is shown below

alternating current(ac)

An alternating current (ac) is a current that varies sinusoidally with time.

A time-varying current is represented by the symbol i.A common form of time-varying current is the sinusoidal current or alternating current (ac).Waveform is shown below

Voltage

Voltage (or potential difference) is the energy required to move a unit charge through an element, measured in volts (V).

The voltage V_ab between two points a and b in an electric circuit is the energy (or work) needed to move a unit charge from a to b; mathematically,

where w is energy in joules (J) and q is charge in coulombs (C). The voltage v_ab or simply v measured in Volt.