Voltage Current and Resistance

An electric circuit is characterized by there main magnitudes: Voltage, Electric current, and Electric Resistance.

Voltage: The voltage at a given point of the circuit is the energy carried by the electrons at that point, is measured in Volts (V). In a electric circuit electrons leave the - terminal of the battery carrying as much energy as the battery's nominal voltage, and come back to the + terminal having spent all their energy, that means, carrying 0 volts of energy.

We normally don't speak of voltage in absolute terms, but of voltage differences between two points of the ciircuit a and b.

Voltage at point a is: Va.

Voltage at point b is: Vb

Voltage difference between a and b is: Vab = Va - Vb.

Electric current: The electric current at a given point of a circuit is the electrons flow rate of at it. Is measured in Amperes. When the current is 1A the electrons flow at a rate of 6,25x10¹⁸ electrons per second. The electrons in a circuit go from the - terminal to the + terminal, but the conventional direction of the electric current is defined for positively charged particles and goes from the + terminal to the - terminal. The electric current remains constant through a wire, it only changes after an intersection.

Resistance: The resistance between two points of a circuit is the opossition to the flow of the electric current between those two points. Is measured in Ohms.

Click on the simulator below to do the exercises at the bottom of the page.