Such a coil. will create a magnetic ï¬eld perpendicular to the magnetic needle. The ï¬eld changes direction in synchrony with the oscillation of the alternating current, so if. the frequency of the current is adjusted to the resonance frequency of the magnetic needle, the. current will set the needle in motion.
A complex number whose real part is zero is said to be purely imaginary, whereas a complex number whose imaginary part is zero is a real number. In this way, the complex numbers contain the ordinary real numbers while extending them in order to solve problems that cannot be solved with real numbers alone.
Numbers like 3 â 2i or that can be written as the sum or difference of a real number and an imaginary number. Complex numbers are indicated by the symbol . Note: All real numbers and all pure imaginary numbers are complex. Sometimes, however, mathematicians use the phrase complex numbers to refer strictly to numbers which have both nonzero real parts and nonzero imaginary parts.