Which of the following denotes the two values of electrical charge a quark can have? (A) Plus one-third 𝑒 and minus two-thirds 𝑒. (B) Zero and one-half 𝑒. (C) Plus one 𝑒 and minus one 𝑒. (D) Minus one-third 𝑒 and plus two-thirds 𝑒. Or (E) plus one-half 𝑒 and minus one-half 𝑒.
Atoms are composed of protons, neutrons, and electrons. Protons and neutrons are composed of particles called quarks. Quarks are subatomic particles with a fractional electric charge and are fundamental constituents of matter. They have a charge just like protons and electrons do. The charge in a proton is the elementary charge represented by the symbol 𝑒. It is sometimes written as plus one 𝑒 and sometimes just plus one. Electrons, on the other hand, have a charge of minus one 𝑒. But this is sometimes written as minus one. The elementary charge is defined as the electrical charge carried by a single proton. It has a value of 1.602 times 10 to the power of minus 19 coulombs.
So we know that the electrical charge on an electron is minus one 𝑒 and on a proton is plus one 𝑒. But a quark has a fractional electric charge. Options (B) and (C) both contain values that are not fractional. So neither (B) nor (C) can be the answer to this question. There are six different types or flavors of quark. They are up, down, charm, strange, top, and bottom. Each quark has an electric charge. Even though there are six different flavors of quark, there are actually only two electric charges that they can have. They’ll either have plus two-thirds 𝑒 or minus one-third 𝑒.
So the answer to the question “Which of the following denotes the two values of electrical charge a quark can have?” is (D) minus one-third 𝑒 and plus two-thirds 𝑒.