Current
· In an electric circuit, an energy source provides electrons with energy.
· Conductors transport the electrons to where the electron energy is transferred, then back to the source to be re-energized.
· Current can be defined as the rate of charge flow and is given the symbol I. The formula for current is the total amount of charge moving past a point in a conductor divided by the time taken.
I=Q/T
I is the current in amperes (A), Q is the charge in coulombs (C), and t is the time in seconds.
· Current is a flow of negatively charged electrons repelling one another.
· On the subject of measuring current, an ammeter must be used. It must be rewired so that all current runs serially through the ammeter.
· In direct current (DC) the current flows in a single direction from the power supply through the conductor to a load, while in alternating current (AC), the electrons periodically reverse the direction of their flow.
· A path for the electric current to flow to and from the power supply is called a circuit and is required for any electrical device to work properly.
Example of an electrical circuit (This is the familiar circuit of a torch battery
Electrical Potential
· An electric charge has a certain amount of electrical potential energy because of the electric field set up by the power supply. The power supply has to increase the electrical potential energy of each coulomb of charge from a low to a high value. As the charge flows through the load, its energy decreases.
· The electrical potential energy for each coulomb of charge in a circuit is called electric potential difference (Voltage)
V=E/Q
E is the energy required to increase the electric potential of a charge, Q.
· A volt (V) is the electrical potential difference between two points if one joule of work (J) is required to move one coulomb (C) of charge between the points.
· Potential difference between any two points can be measured using a voltmeter.
Example of a voltmeter
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