Class 10 Physics Unit 16 – Basic Electronics helps students learn the basics of electronics in an easy way. It explains thermionic emission, which is when electrons come out from a heated metal, and the properties of electrons, like their charge and mass. Students also learn about the Cathode-Ray Oscilloscope (C.R.O), which shows electrical signals on a screen. The unit talks about analogue and digital electronics, where analogue signals are continuous and digital signals are 0s and 1s. It also teaches logic gates like AND, OR, NOT, NAND, and NOR, and how they are used in computers, calculators, and digital devices. This unit is very helpful for students to understand electronics clearly and prepare for exams easily.
Important MCQs – Unit 16 Basic Electronics
1. The process by which electrons are emitted by a hot metal surface is known as:
(a) Boiling
(b) Evaporation
(c) Conduction
(d) Thermionic Emission ✅
2. Cathode rays are:
(a) Protons moving from anode to cathode
(b) Neutrons moving randomly
(c) Electrons emitted from cathode ✅
(d) Ions produced by chemical reaction
3. Who discovered that cathode rays are deflected by electric and magnetic fields?
(a) Rutherford
(b) Newton
(c) J.J. Thomson ✅
(d) Faraday
4. What is the main purpose of a Cathode-Ray Oscilloscope (C.R.O)?
(a) To measure temperature
(b) To store energy
(c) To display changing electric currents or potentials ✅
(d) To control current flow
5. What is the Boolean expression of a NAND gate?
(a) X = A + B
(b) X = A · B
(c) X = (A · B)′ ✅
(d) X = A
Short Questions – Unit 16 Basic Electronics
1. What is thermionic emission?
Answer:
Thermionic emission is the process by which electrons are emitted from the surface of a hot metal.
Explanation:
When a metal is heated, its electrons gain enough energy to leave the metal’s surface. This principle is used in devices like vacuum tubes and Cathode-Ray Oscilloscopes (C.R.O).
2. What are cathode rays?
Answer:
Cathode rays are streams of electrons emitted from the hot cathode surface that move toward the anode due to a potential difference.
Explanation:
Cathode rays travel in straight lines and can produce fluorescence on a screen. They are used in Cathode-Ray Oscilloscopes (C.R.O), old television tubes, and other electronic devices.
3. Who discovered cathode rays and what did he conclude?
Answer:
J.J. Thomson discovered cathode rays in 1897 and concluded that they consist of negatively charged particles called electrons.
Explanation:
Through his experiments, Thomson also measured the charge-to-mass ratio of electrons, proving that electrons are tiny, negatively charged particles present in all atoms.
4. Name the particle discovered by J.J. Thomson.
Answer:
J.J. Thomson discovered the electron.
Explanation:
Electrons are negatively charged subatomic particles present in all atoms. Thomson’s discovery of the electron was a key step in understanding atomic structure and electronics.
Long Questions – Unit 16 Basic Electronics
Q1: Explain J.J. Thomson’s experiment for the discovery of electron using cathode rays.
Introduction:
In 1897, Sir J.J. Thomson, a British physicist, performed a famous experiment to study cathode rays. This experiment led to the discovery of electrons, the first subatomic particle to be identified. It proved that atoms are not indivisible, as was previously believed.
Apparatus Used:
-
Discharge tube: A glass tube containing low-pressure gas.
-
Electrodes: Cathode (negative) and Anode (positive) inside the tube.
-
High-voltage power supply: To create a potential difference between the electrodes.
-
Electric and magnetic fields: Applied externally to observe deflection of rays.
-
Fluorescent screen: To detect the position of cathode rays.
Procedure & Observations:
-
Emission of Cathode Rays:
-
When a high voltage is applied, cathode rays are emitted from the cathode and travel in a straight line toward the anode.
-
The rays are invisible but produce a bright spot when they strike the fluorescent screen.
-
-
Effect of Electric Field:
-
When an electric field is applied across the tube, the rays are deflected toward the positive plate, proving that the rays are negatively charged.
-
-
Effect of Magnetic Field:
-
When a magnetic field is applied, the rays are also deflected.
-
This confirms that cathode rays are charged particles, not light or energy waves.
-
Conclusion by J.J. Thomson:
-
Cathode rays consist of tiny negatively charged particles.
-
These particles are much lighter than atoms.
-
Thomson named these particles electrons.
Significance of the Experiment:
-
First proof that atoms are divisible.
-
Discovery of the electron laid the foundation of atomic structure and modern physics.
-
Helped in understanding electricity, electronics, and subatomic particles.
Download PDF
Download the complete chapter notes in PDF for easy learning and quick exam revision.
English Medium View English Medium
Urdu Medium View Urdu Medium PDF