Electric Current Basics

Study Notes

Electric current is the flow of electric charges through a conductor, requiring a potential difference between its terminals.

Conventional Current: Defined as the flow of positive charges from positive (+) to negative (-) pole; this direction is used throughout the syllabus.
Electronic Current: Refers to the flow of electrons from negative (-) to positive (+) terminal.

An electric source is needed to create a potential difference between two terminals of a conductor.
A closed circuit allows for the continuous flow of electric current.

Electric Current Intensity (I): Measured in Amperes (A), calculated as the quantity of electric charges (Q) passing through a cross-sectional area per second.
Electric Potential Difference (P.D): The difference in electric potential between two points in a circuit.
Electrical Resistance (R): The opposition to the flow of electric current in a conductor.

Current intensity is calculated using the formula:
[ I = \frac{Q}{t} ]
Where Q is the quantity of charges in coulombs, and t is the time in seconds.
Rearranged, this means:
[ Q = I \times t ]

An Ampere is the current intensity produced by the passage of one coulomb of charge through a conductor in one second.

Electric current intensity is measured using an Ammeter, which is connected in series within the circuit.

Problem 1: With a current intensity of 3.2 A over 3 seconds:
[ Q = I \times t = 3.2 , A \times 3 , s = n \times 1.6 \times 10^{-19} ]
Results in ( n = 6 \times 10^{19} ) electrons.
Problem 2: For an electron rotating around a hydrogen nucleus at 6.6 x ( 10^{15} ) revolutions per second:
[ I = 6.6 \times 10^{15} \times 1.6 \times 10^{-19} = 10.56 \times 10^{-14} , A ]
Problem 3: For flow rates of electrons in wires:
Wire X: ( 10^{20} ) electrons/sec; Wire Y: ( 2 \times 10^{20} ) electrons/sec.
Results in a current intensity ratio ( \frac{I_x}{I_y} = \frac{1}{2} ).

Problem 4: Based on the Bohr model, an electron moves in a circular path with a radius of 0.53 A0 and a speed of ( 2.2 \times 10^{6} , m/s ); calculation of the current intensity resulting from this motion is required.