ELECTRIC CURRENT Electric current (I) is the flow of electric charge.
It’s a scalar quantity with an SI unit of ampere (A).1
The current is 1 ampere when 1 coulomb of (electric) charge moves through each point in a circuit per second. 1 A 1 C s1 Current can also be referred to as amperage, as it is measured in amps.
current Using symbols, the equation is
total charge passing a point time taken
I Q t
ELECTRIC CURRENT
Q It Q charge, I current, t time
I is used as the symbol for current as André Ampère originally called current ‘intensité’, which is French for ‘intensity’. Current was originally referred to as ‘electrical intensity’; however, that expression is no longer in use.
Measuring Current An ammeter is used to measure current.
In order to measure the current flowing through a component the ammeter is connected in series with that component.
Smaller currents are measured with milliammeters or microammeters.A galvanometer is another word for a milliammeter or microammeter.
The circuit symbols for an ammeter, a milliammeter, a microammeter and a galvanometer are:
Ammeter A
Milliammeter mA
Microammeter A
1The definition of the Ampere involves electromagnetic forces; it is dealt with in Chapter 20. CURRENT ELECTRICITY 291 Galvanometer
LUIGI GALVANI, 1738–98 (ITALIAN)
While conducting experiments with static electricity he discovered that the muscles of dead frogs twitched when struck by a spark.This finding provided the basis for the current understanding of electrical energy.The device for measuring small electrical currents bears his name: galvanometer.
