Physics 10 class Chapter 16 Introductory Electronics Conceptual Questions, shrot question, long question, pdf downalod for all kpk boards.
Physics 10 class Chapter 16 Introductory Electronics
Table of Contents
What are free electrons?
Free electrons are those electrons that are not bound to a particular atom and free to move randomly through the metal /conductor as a whole.
What is the function of an accelerating anode in an electron gun?
The electrode beam is accelerated towards the focusing anode via an accelerating anode.
If the electron beam in a television tube is striking just one point on the screen at a time, how can we get a full picture? Explain.
Some television sets and some computer display monitors have a cathode ray tube inside it. An electron gun sends a narrow beam of high-speed electrons toward the screen of the tube. The inner surface of the screen is covered with a phosphor coating, and when the electrons strike it, they generate a spot of visible light. This spot is called a pixel (a ‘picture element’).
To create a black-and-white picture, the electron beam is scanned on the whole screen in sawtooth shape. (b)
As the beam scans the screen brighter and draker spots are created by controlling electrons emitted from electron gun. A color TV operates with three electron guns i.e red, green and blue colors. (b) Red, green and blue are primary colors, so virtually all other colors can be created by varying the intensities of the three beams focused on a cluster.
Why image is distorted when a magnet is brought close to old television screens or monitors with a cathode ray tube (CRT) inside?
A magnet distorts the picture as it distorts the path of electrons flowing from the electron gun towards the screen inside the television screen. As electrons are negatively charged particles, their motion is distorted by a magnet.
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Q.5) Assuming that cathode rays are a beam of charged particles, how could you demonstrate that these particles are negatively charged? Explain.
Answer:
a. Deflection by Electric beam
As cathode rays are a beam of negatively charged particles, it can be attracted by a positive electrode and repelled by a negative electrode.
b. Deflection by Magnetic Field:
Since ‘cathode rays’ is a stream of electrons, which are negatively charged, a magnetic field exerts forces on electrically charged particles that are in motion in any direction other than that of the magnetic field. To determine the direction of the force and thus the deflection of the electron beam, the same right-hand rule or fleming left-hand rule can be used.
Q.6) If there are 4 inputs in any logic gate, how many combinations are possible?
Answer:
a binary (2-state) device having 4 inputs have 16 combinations possible.
As 24= 16
Q.8) What are the algebraic Boolean expressions to represent the output of AND OR, NOT, NAND and NOR gates?
Answer:
AND Gate:
X= A.B
or just
X=AB (which is read as ‘X equals A AND B’)
OR Gate:
X= A + B (which is read as “X equals A OR B”)
NOT Gate:
X=NOT A
NAND Gate:
NOT (A and B)
NOR Gate:
X equals not [A or B]
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Comprehensive Questions Physics Class 10 Notes pdf
Q.1) Why electrons are emitted from an electrically heated metal filament?
Answer:
If we increase the temperature of the metal, electrons start to move faster and some may have the energy to escape from the metal. The higher the temperature, the higher will be the number of escaping electrons.
Q.2) What are cathode rays? How are cathode rays produced?
Answer:
Electron beam produced by electron gun is also called cathode rays as these rays are emitted from a negative electrode, also termed as cathode.
Electron gun consists of a glass tube at very low pressure, with negatively charged electrode as cathode.
The electrons are emitted through the indirectly heated cathode. Indirectly heated cathode means the cathode surrounds the filament and emit electrons when the filament is heated by the power applied. For getting the high emission of electrons at the moderate temperature, the layer of barium and strontium oxide is applied at the end of cathode.
Q.3) Describe the construction and working of electron gun?
Answer:
The electron gun is a source of focused and accelerated electron beam. Electron gun is a versatile electrical component. It is an essential part of a number of devices, like Televisions, 3D printers, Scanning ELectron microscopes (SEM) and Large synchrotrons.Electron gun consists of a glass tube at very low pressure, with the negatively charged electrode as the cathode and positively charged electrode as anode as shown below. The electrons are emitted through the indirectly heated cathode. Indirectly heated cathode means the cathode surrounds the filament and emit electrons when the filament is heated up by the power applied. For getting the high emission of electrons at the moderate temperature, the Layer of barium and strontium oxide is applied at the end of the cathode. The current and voltage required by the indirectly heated cathode are approximately equal to the 600 mA and 6.3 V.
After exiting from the cathode, the electron passes through the control grid. The control grid is mostly made up of nickel material. The grid has negative biasing which controls the flow of electrons.
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By increasing the negative bias, one can decrease the number of electrons passing
through and vice versa, thereby controlling the intensity (number of electrons) of
the electron beam.
The electron which passes from the control grid is accelerated by the high positive
potential which is applied across the accelerating anode. The electron beam is
focused by the focusing anode.
The beam after passing through the focusing anode passes through the deflection
system and goes to the fluorescent screen.
Q.5) Describe the working principle of Cathode Ray Oscilloscope (CRO) and make list of its uses.
Answer:
CATHODE RAY OSCILLOSCOPE (C. R. O.)
The Cathode Ray Tube (CRT) is used in computer monitors, TV sets and oscilloscope tubes. The main part of the C. R. O. is a highly evacuated glass tube, consisting of parts which generate a beam of electrons, accelerates them, shapes them into a narrow beam, and provides external connections to the sets of plates for changing the direction of the beam.
The CRO operates by firing an electron beam at a fluorescent material, which give
off light as shown below. It consists of the following parts:
a) Electron gun :
The electron beam is generated at the cathode in the electron gun. As described earlier in the electron gun, potential (voltage) is applied, which strips off and accelerates the electrons by accelerating anode.
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The electrons then travel to the electron beam focusing anode. An electrostatic mechanism is used to focus the beam.
b) Deflection system :
After the beam exits from the electron gun, it travels to the electron beam deflector. The deflector has two mechanisms, one to change the vertical direction and one to change the horizontal direction of the beam. This allows the electron beam to sweep over the entire screen.
c) Screen When an electron in the beam strikes a phosphor (such as Zinc Sulphid ZnS). It excites an electron in the phosphor. After being excited, the electron then releases the energy it got in form of a visible light, which is always the same for that phosphor. Phosphors emitting red, blue, and green light form a color image. The Cathode Ray Oscilloscope (CRO) is an electronic test instrument, used to observe the waveform of a repetitive electric signal. This signal can be amplified or attenuated as required. Which enable its user to get useful information about the electrical component attached to its input terminal.
Uses of Cathode Ray Oscilloscope:
In a laboratory, a Cathode Ray Oscilloscope (CRO) can be used to :
1. display different types of wave form.
2. measure short time interval.
3. measure potential difference (as a
voltmeter).
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One of the most frequent uses of an oscilloscope is troubleshooting a malfunctioned electronic equipment because it has the advantage that it can graphically show signals. Using a voltmeter to study a circuit may show a totally unexpected intermediate voltage. An oscilloscope, on the other hand, can show the changes in the circuit voltage at various instants (showing that the circuit is oscillating). In such cases, the precise shape or timing of a pulse is important to troubleshoot the equipment.
Another use of oscilloscope is to check newly designed circuitry. very often a newly designed circuit will misbehave because of design errors, bad voltage Levels, electrical noise etc.
Q.6) What is the difference between analogue and digital electronics?
Answer:
Analogue Electronics:
Analogue quantity is the one having continuous values. Therefore analogue signal is a continuously varying electrical quantity.
“The branch of electronics which processes the data being provided in the form of analogue quantities is called analogue electronics.”
Digital electronics:
Digital systems, on the other hand, operate on discrete digits that represent numbers, letters, or symbols, They deal strictly with ON and OFF states, which we can represent by 0s and 1s.
“The branch of electrons which processes the data being provided in the form of digits is known as digital electronics.”
Q.8) Explain simple uses of logic gates in
(a) automatic light bulb switching
(b) textile coloring plant.
Answer:
a) Automatic light bulb switching:
If you desire to automatically switch the street lights on and off, after appropriate time and light level, you can use an AND Gate.
During the day when tight shines on Light Dependent Resistor (LDR), the resistance is high and current in the wire is low (0). In the evening when the light fades out, the resistance of LDR decreases and it starts conducting and turns to high (1). But the light will not glow until the timer time is not reached after which it would also turn high (1). When both the terminals are high the street light wilt turn up. The schematic representation is shown below in (a). On the other hand, if we want to turn the light on when either light is Low or timer time is reached, we can use an OR gate, as below in (b).
(b) Textile coloring plant:
A textile coloring pLant uses two tanks to store red color and green color. Each tank has a sensor that detects when the color level drops to 25% of full. The sensors produce a high level of 5 V when the tanks are more than one-quarter full. When the volume of color in a tank drops to one-quarter full or less, the. sensor puts out a low level of 0 V. Manufacturer requires that an alarm is raised when both tanks are more than one-quarter empty. A NOR gate with its two inputs connected to the tank level sensors and its
output connected to the indicator alarm system is shown below. Such that if the red color
tank and green color tank are above one-quarter full, the signal is low (0 V), even if one
tank reduces to less than 25 % of full.
As soon as both sensor outputs are low (o v), indicating that both tanks are Less than one-quarter full, the NoR gate output is high (5 v) and the alarm is raised. Here NAND gate circuitry can be used to indicate by a green tight that both tanks are full.
