The basic unit of current in the international system of units is ampere. 1 amp is defined as: two infinite parallel straight lines with a distance of 1 m in vacuum are energized with equal constant current. When the force acting on each meter of conductor is 2× 10-7 N, the current on each conductor is 1 amp. The definition of 1 amp in primary learning: the amount of charge passing through the conductor section in 1 sec is 1 coulomb, that is, 1 amp = 1 coulomb/sec.

Conversion method:

1kA= 1000A

1A= 1000mA

1mA= 1000μA

1μA= 1000nA

1nA= 1000pA

Some common currents: electronic watch 1.5μA to 2μA, incandescent bulb 200mA, mobile phone 100mA, air conditioner 5A to 10A, high voltage 200A, lightning 20000A to 200000A.

Definition formula: q is the amount of charge passing through the cross section of a conductor, and the unit is coulomb. T is the time for the charge to pass through the conductor, and the unit is seconds.

In the international system of units, the main unit of voltage is volt (V), which is denoted by the symbol V. [1] 1 volt is equivalent to the work per 1 coulomb charge, that is, 1 volt = 1 joule.

The transformation relationship between them is:

1kV= 1000V

1V= 1000mV

1mV= 1000μv