Electronic Devices - Online Test

Answer : Option C
Explaination / Solution:

Biasing is the application of a voltage across a p–n junction.

When we connect p-type region of a junction with the positive terminal of a voltage source and n-type region with the negative terminal of the voltage source, then the junction is said to be forward biased.

At this condition, due to the attraction of positive terminal of source, electrons which participated in covalent bond creations in p-type material, will be attracted towards the terminal.

Answer : Option C
Explaination / Solution:

A transistor consisting of two p-n junctions combined to form either an n-p-n or a p-n-p transistor, having the three electrodes, the emitter, base, and collector

Answer : Option A
Explaination / Solution:

A transistor is an electronic component that can be used as an amplifier, or as a switch. It is made of semiconductor material. Transistors are found in most electronic devices. 

A transistor has three connectors or terminals. In the older bipolar transistor they are the collector, the emitter, and the base. The flow of charge goes in the collector, and out of the emitter, depending on the charge flowing to the base

Answer : Option B
Explaination / Solution:

If a pentavalent element from the Vth Group such as Antimony (Sb) is added to pure geranium (Ge) or silicone (Si), then four electrons of (Sb) will form covalent bonds with four (Ge) or (Si) atoms. The fifth electron of 'Sb' is free to move which makes (Ge) or (Si) a good conductor. This type of material is called n-type substance.

Answer : Option C
Explaination / Solution:

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material usually with at least three terminals for connection to an external circuit. The first practically implemented device was a point-contact transistor invented in 1947 by American physicists John Bardeen, Walter Brattain, and William Shockley. The transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios, calculators, and computers, among other things. The transistor is on the list of IEEE milestones in electronics, and Bardeen, Brattain, and Shockley shared the 1956 Nobel Prize in Physics for their achievement.

Answer : Option A
Explaination / Solution:

When the p-type crystal is grown between relatively wide sections of n-type crystals then the transistor is called NPN transistor.

Answer : Option D
Explaination / Solution:

Current gain of transistor

β=△Ic△Ib=(18−10)×10−3A(200−100)10−6A=8×10−3100×10−68×10−310−4=80

Answer : Option C
Explaination / Solution:

In P-type doping, boron or gallium is the dopant. Boron and gallium each have only three outer electrons. When mixed into the silicon lattice, they form "holes" in the lattice where a silicon electron has nothing to bond to. The absence of an electron creates the effect of a positive charge, hence the name P-type. Holes can conduct current. A hole happily accepts an electron from a neighbor, moving the hole over a space. P-type silicon is a good conductor.

Answer : Option C
Explaination / Solution:

Amplifier is an electronic device. The device which increases the value of a signal is called amplifier. In input a weak signal is applied, in output a strong, same shape signal is gained. Amplify means to increase the value of something.

The collector is reverse biased and the emitter is forward biased while using transistor as an amplifier.

Answer : Option C
Explaination / Solution:

When a diode is connected in a Reverse Bias condition, a positive voltage is applied to the N-type material and a negative voltage is applied to the P-type material.

The positive voltage applied to the N-type material attracts electrons towards the positive electrode and away from the junction, while the holes in the P-type end are also attracted away from the junction towards the negative electrode.

The net result is that the depletion layer grows wider due to a lack of electrons and holes and presents a high impedance path, almost an insulator. The result is that a high potential barrier is created thus preventing current from flowing through the semiconductor material