Physics Quiz

What is the charge of an electron?

• +1.6 × 10⁻¹⁹ C

• –1.6 × 10⁻¹⁹ C

• 0 C

• +3.2 × 10⁻¹⁹ C

Answer explanation

The charge of an electron is –1.6 × 10⁻¹⁹ C, which is a fundamental constant in physics. This negative charge distinguishes electrons from protons, which have a positive charge of +1.6 × 10⁻¹⁹ C.

Which particle is responsible for current conduction in metals?

• Protons

• Neutrons

• Electrons

• Holes

Answer explanation

Electrons are the primary charge carriers in metals, allowing for current conduction. Protons and neutrons are found in the nucleus and do not contribute to electrical conduction, while holes refer to the absence of electrons in semiconductors.

In a semiconductor, a hole is defined as:

• A missing neutron

• A positive ion

• A vacant electron state in the valence band

• A free proton

Answer explanation

In a semiconductor, a hole represents a vacant electron state in the valence band, indicating the absence of an electron. This absence behaves like a positive charge carrier, but it is not a physical particle like a proton or ion.

Which of the following has the smallest mass?

• Neutron

• Proton

• Electron

• Alpha particle

Answer explanation

The electron has the smallest mass among the options. A neutron and proton have similar masses, significantly larger than that of an electron, while an alpha particle, composed of two protons and two neutrons, has an even greater mass.

The atomic number of an element is determined by the number of:

• Neutrons

• Electrons

• Protons

• Nucleons

Answer explanation

The atomic number of an element is defined by the number of protons in its nucleus. Electrons and neutrons do not determine the atomic number, while nucleons refer to both protons and neutrons collectively.

Which orbit in the Bohr model of hydrogen has the lowest energy?

• n = 1

• n = 2

• n = 3

• n = ∞

Answer explanation

In the Bohr model, the energy levels are quantized, with n = 1 being the closest to the nucleus and having the lowest energy. Higher n values (n = 2, n = 3) correspond to higher energy levels, while n = ∞ represents ionization.

What is the maximum number of electrons that can be accommodated in the L shell?

• 2

• 4

• 8

• 18

Answer explanation

The L shell corresponds to the second energy level (n=2) and can hold a maximum of 2n² electrons. Thus, 2(2)² = 8 electrons can be accommodated in the L shell, making 8 the correct answer.

In an intrinsic semiconductor, the number of electrons is:

• Greater than holes

• Less than holes

• Equal to the number of holes

• Zero

Answer explanation

In an intrinsic semiconductor, the number of electrons generated is equal to the number of holes created due to thermal excitation. Therefore, the correct answer is that the number of electrons is equal to the number of holes.

Which of the following is not a fundamental particle of an atom?

• Proton

• Electron

• Photon

• Neutron

Answer explanation

The photon is not a fundamental particle of an atom; it is a force carrier for electromagnetic interactions. In contrast, protons, electrons, and neutrons are the fundamental particles that make up an atom.

The movement of which type of charge carrier is dominant in P-type semiconductors?

• Electrons

• Neutrons

• Holes

• Ions

Answer explanation

In P-type semiconductors, the dominant charge carriers are holes, which are created when electrons are absent from the valence band. This results in positive charge carriers, making holes the primary charge carriers in P-type materials.