Question

$1$ microampere = ______ ampere.
(A) ${10}^{-3}$
(B) ${10}^{-6}$
(C) ${10}^6$
(D) ${10}^3$

Answer 1

Hint: The prefix of the unit indicates the value of the multiplier that must be multiplied with the given unit. Using this we can obtain the value of one ampere in terms of micro amperes. On modifying that relation we will get the required answer.

Complete step-by-step solution
The unit prefix indicates the value of the multiplier to be multiplied with the given unit, with which the prefix is added. The prefix “micro” denotes a sixth. It is smaller than the original unit by the sixth power of ten. So this means that there must be ten raised to the power six micro amperes, or one million micro amperes in one ampere. This statement can be mathematically written as
 $1\text{A}={10}^6\mu \text{A}$
Dividing by ${10}^6$ on both the sides, we get
 $1\mu \text{A}={10}^{-6}\text{A}$
So there are ${10}^{-6}$ amperes in one micro – ampere. Thus, we can say that
 $1$ micro - ampere $={10}^{-6}$ ampere.
Hence, the correct answer is option B.

Additional information
Along with micro, there exist many other prefixes in units and measurements. All of them are used to indicate the values of the multipliers with the units with which they are being used. Below is the list of some commonly used prefixes and their corresponding multiplier values.

Prefix	Multiplier
Milli	${10}^{-3}$
Macro	${10}^{-6}$
Centi	${10}^{-2}$
Nano	${10}^{-9}$
Fermi	${10}^{-15}$
Deci	${10}^{-1}$
Kilo	${10}^3$
Mega	${10}^6$
Giga	${10}^9$
Pico	${10}^{-12}$

Note
The meaning of the prefix “micro” is small. It is used in representing the dimensions of the quantities which are small. For example, it is used in the measurements of the diameter of bacteria and the cells.