Understanding the Charge on an Electron

Electrons are fundamental particles that carry an electric charge. The charge on a single electron is a fixed and fundamental constant in physics.

The magnitude of this fundamental charge, often denoted as \(e\), is approximately \(1.602 \times 10^{-19}\) Coulombs (\(\text{C}\)). However, electrons carry a negative charge, while protons carry a positive charge of the same magnitude.

Therefore, the exact charge on an electron is \( -1.602 \times 10^{-19} \, \text{C} \). The value given in the options is \(1.6 \times 10^{-19}\) Coulomb, which is the magnitude of the elementary charge, rounded to two significant figures.

Let's evaluate the given options based on this knowledge:

• Option 1: \(+ 1.6 \times 10^{-19}\) Coulomb. This is the magnitude but with a positive sign. Electrons are negatively charged, so this option is incorrect for the charge on an electron, although it is the charge on a proton.
• Option 2: \(1.6 \times 10^{-19}\) Coulomb. This option gives the correct magnitude of the charge. Although the negative sign is missing, in the context of multiple-choice options where the correct magnitude is provided, this is often considered the intended answer representing the magnitude of the electron's charge.
• Option 3: \(+ 1.9 \times 10^{-16}\) Coulomb. The magnitude (\(1.9 \times 10^{-16}\)) is incorrect, and the sign is positive, which is wrong for an electron.
• Option 4: \(1.9 \times 10^{-16}\) Coulomb. The magnitude (\(1.9 \times 10^{-16}\)) is incorrect.

Comparing the options with the known value of the electron's charge, option 2 provides the correct magnitude \(1.6 \times 10^{-19}\) Coulomb.

Revision Table: Elementary Charge

Additional Information: Electric Charge Concepts

Electric charge is a fundamental property of matter. There are two types of electric charge: positive and negative.

• Elementary Charge: The smallest unit of positive charge observable in ordinary matter is carried by the proton, and the smallest unit of negative charge is carried by the electron. The magnitude of this charge is called the elementary charge, \(e\).
• Quantization of Charge: Electric charge is quantized, meaning it exists in discrete packages. Any observable charge is an integer multiple of the elementary charge \(e\). For example, the charge on any object is \(Q = ne\), where \(n\) is an integer (\(n = 0, \pm 1, \pm 2, \dots\)).
• Conservation of Charge: The total electric charge in an isolated system remains constant over time. Charge cannot be created or destroyed, only transferred between objects.

Understanding the value and nature of the charge on an electron is crucial for studying electricity, magnetism, and atomic physics.