Q1. Define following terms:
A property of a particle by which it may repel or attract other particles that have a charge of similar or opposite sign.
A flow of positive electric charge. The strength of current flow in any medium is related to voltage differences in that medium, as well as the electrical properties of the medium and is measured in amperes. Since electrons are stipulated to have a negative charge, current in an electrical circuitactually flows in the opposite direction of the movement of electrons.
A measure of the difference in electric potential between two points in space, a material or an electric circuit, expressed in volts.
A property of aconductor by virtue of which the passage of current is opposed, causing electric energy to be transformed in to heat: equal to the voltage across the conductor divided by the current flowing in the conductor: usually measured in ohms.
Q2. Differentiate between Electrical & Electronics engineering. Electrical Engineering is the branch of engineering concerned with the practical applications of electricity in all its forms, including those of the field of electronics.
Electronics engineering is that branch of electrical engineering concerned with the uses of the electromagnetic spectrum and with the application of such electronic devices as integrated circuits, transistors, and vacuum tubes.
Q3. Differentiate between electric conductors & insulators.
In a metallic conductor such as copper, the atoms are arranged in a regular array called a crystal lattice. The electrons in the outer orbits of each metal atom are only loosely bound to the nucleus. These electrons are not closely associated with any particular atom and are free to move through the crystal lattice. Once an electron has left its orbit around a particular atom, that atom is left with an excess positive charge. The electron-deficient atom is called a positive ion. The electron that is now free to move is called a free electron. The free electrons in a conductor can be visualized as a cloud of electrons surrounding fixed positive ions. At normal temperatures, the ions possess energy and vibrate. Collisions between vibrating ions and free electrons cause the electrons to move in a random manner. Over a long period of time, the net motion of these free electrons is zero.
If an electric field is applied to the conductor, the free electrons will acquire additional energy and will tend to move in the direction dictated by the field. There will be a resulting net motion of free electrons. The net motion of charge carriers constitutes an electric current. Insulators
In an insulator, nearly all electrons are very tightly bound to their respective atoms. There are practically no electrons that are able to move under the influence of an applied electric field. Therefore, an insulator cannot conduct any appreciable electric current under normal conditions.
Q4. Write a note on pn-junction diode.
Imagine that a p-type block of silicon can be placed in perfect contact with an n-type block. Free electrons from the n-type region will diffuse across the junction to the p-type side where they will recombine with some of the many holes in the p-type material. Similarly, holes will diffuse across the junction in the opposite direction and recombine.
The recombination of free electrons and holes in the vicinity of the junction leaves a narrow region on either side of the junction that contains no mobile charge. This narrow region which has been depleted of mobile charge is called the depletion layer. It extends into both the p-type and n-type regions. Note that the diffusion of holes from the p-type side of the depletion layer leaves behind some uncovered fixed negative charges (the acceptor ions). Similarly, fixed positive charges (donor ions) are uncovered on the n-type side of the depletion layer. There is...
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