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.
1 The integer zero is neutral. 2  It is neither positive nor negative. 3  The sign of an integer is either positive (+) or negative (-), except zero, which has no sign. 4  Two integers are opposites if they are each the same distance away from zero, but on opposite sides of the number line.