electric current

 Is made up of moving electron charge.
 A light will come on immediately when
the pathway is complete because the wires
are already full of electrons and every
electron that leaves the negative terminal
of the battery pushes the one ahead of it.
 The electric potential or voltage is the electrical energy that an electron
possesses. As the electrons move through the circuit, they release their electrical
energy to the electrical load(s) in the circuit.
 Potential difference (or voltage drop) refers to the loss of electric potential as an
electron moves through a circuit. It is measured in volts.
 In a dry cell, a chemical reaction occurs,
and the stored energy released by the
reaction exerts a force on the electric
charges and pushes a certain number of
them on to the terminals of the dry cell.
An excess of electrons accumulates on
the negative terminal, thus giving it a
negative charge, and a matching number
of positive charges remain on the
positive terminal.
 Electrons can be released with their electric potential energy in a circuit only
when the switch is closed and electrons can flow completely around the circuit.
 Electric current refers to the amount of charge that passes a point in a
conducting wire every second.
Current ( I ) 
Charge moving past a point (Q )
Time (t )
Q = charge, measured in coulombs (C)
I = current, measured in amperes (A)
t = time, measured in seconds (s)
One coulomb of charge (1 C) is equal to the amount of charge on
6.25×1018 electrons.
 An ammeter is an instrument that is used to measure
electric current.
Potential difference (V ) 
Energy ( E )
Charge (Q )
E = energy, measured in Joules (J)
V = potential difference, measured in volts (V)
Q = charge, measured in coulombs (C)
 A voltmeter is an instrument that is used to measure potential difference
between two points in a circuit.