To make this calculation, one has to know the conversion equivalents between these two units. The relationship states that 1 amp is equal to 1 milliamp divided by 1000 milliamps per amp, or A = mA/1000. From this relationship, one can substitute 500 for mA, or 500/1000 that also is 0.5. This is equal to the number of amps.
Converting from amps to milliamps, one can use the equation milliamp = 1000 milliamps per amp x amp, or mA = 1000 x A. If one substitutes 0.5 amp for A into this equation, one finds that mA= 1000 x 0.5 = 500.Learn more about Measurements