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Can you say whether a signal is periodic or nonperiodic by looking at its frequency domain plot?
Yes. The Fourier transform of a signal to the frequency domain will give rise to a graph that has energy (is greater than zero) at only the base frequency and its harmonics.
What is the greatest common multiple of 2 and 9?
In any list that includes zero, the answer is zero.
What numbers are between -34 and 58?
That's an infinite list. Zero is on it.
What are the five multiples of 11 that are greater than zero?
They are infinite. The first five are: 11, 22, 33, 44, 55.
What does bias mean in a valve--tube-- radio receiver circuit?
Like many electronic devices, tubes (aka valves) are closer to linear in certain operating ranges--meaning the output is a scaled version of the input when operating in the linear region. However, these linear regions are not typically at zero volts. So a DC bias is added to the AC input signal, shifting the signal into the linear region of the device. The DC bias can be removed from the output, leaving the amplified signal. Essentially the bias shifts the "zero" point for the signal to match the amplifier characteristics. Choosing bias is an important consideration in amplifier design. Amplifiers are designated by a "class" according to their bias--class A, class B, class AB, class C (there are other classes but they aren't used with tubes). Because the bias signal is the zero signal input, the bias determines how much power the tube uses when idle. For example, a class A amplifier is biased to the middle of the tube operating range so it uses about 50% power when idle, which is wasteful and makes a lot of heat.
