ELECTRONICS DEVICES AND CIRCUITS IMP QUESTIONS FOR Iyear JNTU KAKINADA

ELECTRONIC DEVICES AND CIRCUITS
UNIT –I

1. Analyse the two dimensional motion of an electron in electric field.
2. A charged particle having charge thrice that of an electron and mass twice that of an electron is accelerated through a potential difference of 50 V before it enters a uniform magnetic field of flux density of 0.02 Wb/m2 at an angle of 25o with the field. Find (a) The velocity of the charged particle before entering the field, (b)Radius of the helical path, and (c) Time of one revolution.
3. Derive the expression for the deflection in a magnetic deflection system. Hence obtain the expression for magnetic deflection sensitivity.
4. Derive the expression for the deflection in an electrostatic deflection system. Hence obtain the expression for electro static deflection sensitivity.
5. a)What is deflection Defocusing? Give the reasons of defocusing.
b) Compare: Electrostatic deflection and magnetic deflection.
c) An electron beam is deflected of 100 degrees when it traverses in uniform magnetic field, 3 cm wide, having a density of 0.6 mT. Calculate: i) The speed of the electrons and ii) The force on each electron. The direction of the beam is normal to that of the flux.
6. What are the main parts of the CRT? Explain briefly with neat sketch and also explain about the various materials used.
7. (a) Derive the expression for trajectory of an electron placed in combined elec- tric(E) and magnetic fields(B). Both the fields are perpendicular to each other and the initial velocity is zero.(b) Explain the terms: Potential, Electron Volt , Charge density and Current density.
8. An electron is injected with an initial velocity Vox of 4 × 106 m/sec halfway between two large parallel plates 0.5 cm apart. The XZ plane is parallel to the plates. There is a voltage of 200V impressed between the plates, and a magnetic field of 10 mwb/m2 perpendicular to the plates, directed from the positive to the negative plate. Where does the electron strike the positive plate and with what velocity?
9. An electron having a speed V0 = 107m/sec is injected in the XY plane at an angle of 300 to the X axis. A uniform magnetic field parallel to the Y-axis and with flux density B = 5.10 mwb/m2 exists in the region. Find the position of the electron in the region. Find the position of the electron in space at t=5 m sec after entering the magnetic field.
10. In a CRT, the electrons emitted are accelerated by a potential of 500V. The length of the deflecting plates is 1.3 cm. Distance between the deflecting plates is 0.5 cm. The distance between the centre of the deflecting plates and the screen is 20 cm. Determine the value of electrostatic deflection sensitivity.
11. In a CRT, the length of deflecting plates is 2cm. The spacing between the plates is 0.6cm. The distance of the screen from the center of the plates is 16cm. Calculate the deflection sensitivity in m/volt if the final anode voltage is:
i. 600V and
ii. 900V
12. An infinitely large parallel plane plates are spaced 0.8 cm apart. The voltage on one of the plates is raised from 0 to 5 V in 1 ns at a uniform rate with respect to the other. After this duration, the potential difference between the plates is suddenly dropped to 0 V and remains the same thereafter. Find
(a) The position of the electron, which started with zero initial velocity from the negative plate, when the potential difference drops to zero volt,
(b) The total time of transit of the electron from the cathode to the anode.
13. Two plane parallel plates A and B are placed 3 mm apart and potential of b is made 200 V positive with respect to plate A. An electron starts from rest from plate A. Calculate
(a) The velocity of the electron on reaching plate B.
(b) Time taken by the electron to travel from plate A to plate B, and
(c) Kinetic energy of the electron on reaching the plate B.
14. In a parallel plate diode, the cathode and anode are spaced 5mm apart and the anode is kept at 200V d.c. with respect to cathode. Calculate the velocity and the
15.

distance travelled by an electron after a time of 0.5ns, when (a) The initial velocity of an electron is zero and (b) The initial velocity is 2×106 m/s in the direction towards the anode.













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