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.
Actually, zero is neither a negative or a positive number. The whole idea of positive and negative is defined in terms of zero. Negative numbers are numbers that are smaller than zero, and positive numbers are numbers that are bigger than zero. Since zero isn't bigger or smaller than itself (just like you're not older than yourself, or taller than yourself), zero is neither positive nor negative.