Question

Which statement is true regarding DC current?
A.
The electrons move back and forth.
B.
There can only be one voltage supplied.
C.
A high voltage current can be transformed into a low voltage current.
D.
A low voltage current can be transformed into a high voltage current.
E.
This is what is sent from the power plants to your home.

Answer 1

Regarding choices C and D when the term "transformed" is used, if it is suggesting the use of "transformers", it would be false. Choice E. is false for the U.S.A and probably most other countries, as AC (alternating current) is distributed from the power plants to residences. Choice A is false as DC implies a single direction. Now that leaves Choice B. I don't like it either but it may be the best. I don't like the :"There can only be one" as there are many DC circuits that have multiple DC voltages applied, Transistor biasing is only one example. Even the old battery operated radios, had both an "A" battery for the filament supply and a "B" battery to provide plat & screen voltages to the tubes.

Answer 2

The true answer is A!

* This is why...
The zig-zag electron
The zig-zag electron
There are two ways to think about a state with a massive Dirac electron: it can
be
• either a Dirac electron on top of |0Di (we refer to is as a literal single
electron),
• or a Dirac electron on top of the sea |GDi (we refer to it as a floating
electron).
These two possibilities are illustrated in Fig.
If we consider the first possibility, and if we look we see that a
state with a massive Dirac electron of momentum ~p and helicity χ can be written
as a superposition of states with positive and negative-energy Weyl particles:

The zig-zag electron
There are two ways to think about a state with a massive Dirac electron: it can
be
• either a Dirac electron on top of |0Di (we refer to is as a literal single
electron),
• or a Dirac electron on top of the sea |GDi (we refer to it as a floating
electron).
These two possibilities are illustrated in Fig. 6.
If we consider the first possibility, and if we look at Eq. (33), we see that a
state with a massive Dirac electron of momentum ~p and helicity χ can be written
as a superposition of states with positive and negative-energy Weyl particles:

Answer 3

You refer to Fig. 6 and Eq. (33), but did not reveal the source from which you cut and pasted the article. Please leave a link to your source. Paul Dirac was indeed a character, and had several theories, but that was what they were theory, not law.