Which of the following are the properties of an electron? 1) Electron is a constituent of cathode ray 2) Electron is a negatively charged particle 3) The mass of the electron is equal to the mass of the proton 4) Electron is deflected by the electric field but not by magnetic field
1 and 2 only
Analyzing Electron Properties
Let's carefully examine each statement about the properties of an electron to determine which ones are correct.
Statement 1: Electron is a constituent of cathode ray
Cathode rays are streams of fast-moving particles that originate from the cathode (negative electrode) and travel towards the anode (positive electrode) in a discharge tube when a high voltage is applied. Experiments conducted by J.J. Thomson demonstrated that these rays consist of negatively charged particles, which he later identified as electrons. Therefore, this statement is correct.
Key takeaway: Cathode rays are essentially beams of electrons.
Statement 2: Electron is a negatively charged particle
Electrons are fundamental subatomic particles. They carry a fundamental unit of negative electric charge, denoted as $-\text{e}$. The magnitude of this charge is approximately $1.602 \times 10^{-19}$ Coulombs. This negative charge is one of the defining properties of an electron. Therefore, this statement is correct.
Key takeaway: The electron possesses a negative charge.
Statement 3: The mass of the electron is equal to the mass of the proton
Protons and electrons are both fundamental particles found in atoms, but they have significantly different masses. The mass of a proton ($m_p$) is much greater than the mass of an electron ($m_e$). Approximately, the mass of a proton is about 1836 times the mass of an electron. So, $m_p \approx 1836 \times m_e$. Therefore, this statement is incorrect.
Key takeaway: Protons are much more massive than electrons.
Statement 4: Electron is deflected by the electric field but not by magnetic field
Electrons are charged particles. Charged particles experience forces when placed in both electric and magnetic fields. An electric field exerts a force $\vec{F}_E = q\vec{E}$ on a charge $q$. A magnetic field exerts a force $\vec{F}_B = q(\vec{v} \times \vec{B})$ on a charge $q$ moving with velocity $\vec{v}$. Since electrons are charged particles ($q = -\text{e}$), they are deflected by both electric fields and magnetic fields (provided they are moving in the magnetic field). Therefore, this statement is incorrect as it claims they are not deflected by a magnetic field.
Key takeaway: Electrons are deflected by both electric and magnetic fields.
Summary of Electron Properties Analysis
Based on the analysis of each statement:
- Statement 1: Correct
- Statement 2: Correct
- Statement 3: Incorrect
- Statement 4: Incorrect
The correct statements are 1 and 2.
Conclusion on Correct Electron Properties
The properties of an electron correctly described in the statements are that an electron is a constituent of cathode rays and that it is a negatively charged particle. The mass of an electron is not equal to the mass of a proton, and electrons are deflected by both electric and magnetic fields, not just electric fields.
Therefore, the statements that are properties of an electron are 1 and 2.
Revision Table: Key Electron Properties
| Property | Description | Correctness of Statement |
|---|---|---|
| Constituent of Cathode Ray | Yes, cathode rays are streams of electrons. | Statement 1 is Correct |
| Electric Charge | Yes, electrons have a negative charge. | Statement 2 is Correct |
| Mass compared to Proton | Electron mass is much smaller than proton mass. | Statement 3 is Incorrect |
| Deflection by Fields | Electrons are deflected by both electric and magnetic fields. | Statement 4 is Incorrect |
Additional Information on Electron Behavior
Electrons are fundamental particles that play a crucial role in electricity, chemistry, and physics. They are found in electron shells surrounding the nucleus of an atom. Their wave-particle duality is a core concept in quantum mechanics.
- Discovery: The electron was discovered by J.J. Thomson in 1897 through his work on cathode rays.
- Charge Quantization: The charge of an electron is the elementary charge, meaning all observable electric charges are integer multiples of the electron's charge magnitude (or proton's charge).
- Spin: Electrons possess an intrinsic angular momentum called spin, which is a quantum property.
- Interactions: Electrons interact via the electromagnetic force.
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