BASIC ELECTRONIC ENGINEERING UNIT I 1. Define Ohm’s law. The ratio of potential difference between any two points of a conductor to the current flowing between them is constant, provided the physical conditions do not change. 𝑉 = 𝐶𝑜𝑛𝑠𝑡𝑎𝑛𝑡 (𝑜𝑟)𝑅 𝐼 2. Define Electric current. The flow of free electrons in a metal or a conductor is called electric current. 3. Define Electric Potential. The electric potential at a point is the amount of work in moving a unit positive charge from infinity to that particular point. The electric potential due to a point charge at a distance r from it is equal to 𝑞 4𝜀0 𝜋𝑟 where 𝜀0 is the permittivity of free space. 4. Define Potential Difference. The amount of energy per unit charge needed to move a charged particle from a reference point to a designated point in a static electric field. It is also stated as the path integral of the electric field over a specified region. The expression is V = ∫E(r).dl. 5. Define magnetic Lorentz Force. Lorentz magnetic force law is the force on a point charge due to electromagnetic fields. If a particle of charge e moves with velocity v in the presence of an electric field E and a magnetic field B, then it will experience a force F. The expression is F = e (v x B). 6. Describe about Cathode ray tube? It is a vacuum tube of special geometrical shape and converts an electrical signal into visual signal. 7. List out the disadvantages of a CRT display? a) Large size and weight. b) High power consumption c) Generates considerable amount of heat while running. d) Geometric distortion. e) Can suffer screen burn-in. 8. Write any four advantages of plasma panel displays. a) High contrast ratio. b) Excellent viewing angle. c) Near zero distortion. d) No geometric distortion.
e) Highly scalable. f) Sub millisecond response time. 9. What is meant by 7 segment display in LCD? A seven-segment display is a form of electronic display device for displaying decimal numerals that is an alternative to the more complex dot matrix displays. 10. Define Electrostatic deflection sensitivity of a CRT. The electrostatic deflection sensitivity is defined as the deflection on screen per volt of deflecting voltage 𝑆= 𝐷 𝑉𝑑 11. Define Magneto static deflection sensitivity of a CRT. The magneto static deflection sensitivity is defined as the deflection on screen per applied magnetic field. 𝑆= 𝐷 𝐵 = 𝑙𝐿 √2𝑉𝑎 𝑒 √𝑚 12. Write the Principle of Television picture tube. Television uses image analysis whereby the scene to be televised is broken up by the camera image sensors into orderly sequence of electrical waves and these are reassembled in their correct position on the viewing screen. 13. Tell about flat panel displays? Flat panel display encompasses a growing numbers of electronic visual display technologies. They are very light and thinner and usually referred as flat screens. 14. Describe a cycloidal path? A cycloidal path is the curve traced by a point on the rim of a circular wheel as the wheel rolls along a straight line. 15. Explain the path of the electron when subjected to a magnetic field. In magnetic field, the electron will move in a circle as the force on the electron will always be at right angles to the electron's motion. In a uniform magnetic field the electron will move in a circle, acceleration is produced but the speed of the electron will remain constant. 16. Define spot deflection of a CRT. Spot deflection is the product of deflection sensitivity and applied voltage of the cathode ray oscilloscope. 17. Explain the resolution of a television picture tube. Resolution quantifies how close lines can be to each other and still be visibly resolved. A tube can resolve pictorial details, if the angle that the details subtend at the eye is not less than 2 minutes of an arc.
18. Tell about scanning in a TV picture tube? It is path over which the image structure is explored and reconstructed on the receiver screen. The pattern is a series of parallel straight lines, each progressing from left to right, following in sequence from top to bottom of the picture. 19. Classify the types of display technology? Display technology is divided into two groups they are volatile and static. 20. List the types of flat panel display. a) Liquid crystal display b) Plasma display panel c) Electroluminescent display d) Vacuum fluorescent display e) Field emission display f) Organic light emitting diodes. 21. Differentiate: Volatile and Static display technologies. S.No Volatile display 1 Requires constant power output to refresh the image on screen any times a second. 2 The pixels need to be refreshed to maintain their state. 3 The image appear steady 4 They don’t depend on the materials Static display They require no energy to maintain the image on the screen. No refreshing is necessary Require energy to change. They rely on materials whose color states are bistable. 22. Compare: LCD and plasma display techniques. S.No LCD 1 Liquid crystal material is filled in between the glass plates. 2 Two point electrodes have been given at the sides of the plate. 3 The electrodes are adjacent to each other. 4 The crystal material will rearrange and transmit or reflect the incident light. Plasma panel display Gas like neon is filled in between the glass plates. It has several parallel electrodes running across the plate The electrodes are right angles to each other. The gas will glow when electric field is applied 23. Define liquid crystals? Liquid crystals are matter in a state that has properties between those of conventional liquid and those of solid crystal. Liquid crystal may flow like a liquid, but its molecules may be oriented in a crystal-like way.
Part B 1. Explain the Behavior of an Electron in an one dimensional and two dimensional Electric field. Also explain the behavior of an electron in a combined electric and magnetic field, parallel to each other. One dimensional electric field: Consider an electron situated between the plates of a parallel plate capacitor as shown in figure. We assume that the electric field is uniform between the plates and d is the distance between the plates. If Vx is the velocity of electron in the X direction, x is the distance travelled by the electron along the X direction. At t = 0, the initial velocity v0x at the initial position x0. Since forces fy and f z are zero, the accelerations ay and az are also zero, hence the electron moves only along the X-direction with constant velocity. The force on an electron in the field is F = -qE From Newton second law F = max Then ax = 𝑞𝐸 𝑚 where E is the magnitude of the electric field. The electron will move in constant acceleration in uniform electric field. (vx − vox) = axt, then vox + axt , ( similar to v = u + at) Again, dx = vxdt,= (vox + axt)dt From equation (1) we can write (1)