C' a brother what important safety precaution must be observed when measuring resistance in an electronic circuit? a. the black test lead must be connected to the chassis ground. b. the red test lead must be at the most positive point in the circuit. c. the meter's highest resistance range setting should be used until the actual value is determined. d. all power to the component under test must be disconnected.

D. All power to the component under test must be disconnected.

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -

The center is basically the heart of it