# Mechatronics Questions and Answers – Solid State Electronic Devices – Thyristors

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This set of Mechatronics written test Questions & Answers focuses on “Solid State Electronic Devices – Thyristors”.

1. How many layers and junctions does an SCR have?
a) Four layers and three junctions
b) Three layers and four junctions
c) Three layers and three junctions
d) Four layers and four junctions

Explanation: An SCR has four layers and three junctions. The layers are the p-n-p-n layer and there are three p-n junctions. There are three terminals named as anode, cathode and the gate terminal. The other options mentioned above are incorrect.

2. An SCR is a ____
a) semiconductor device
b) full conductor device
c) inductor device
d) bidirectional device

Explanation: SCR is a Semiconductor device. It is made up of silicon. As the conduction takes place only in a single direction, an SCR is a unidirectional device. The other options are incorrect.

3. An SCR is a bidirectional device.
a) True
b) False

Explanation: In an SCR, the conduction takes place in a single direction, therefore the SCR is called as a unidirectional device. It is also called a Semiconductor device as it is made up of silicon.

4. The SCR is controlled through ____
a) anode
b) cathode
c) gate
d) anode and cathode

Explanation: The SCR is controlled through the gate. It is a current controlled device. The anode is always positive with respect to the cathode and the direction of forwarding voltage is from anode to cathode.

5. What is the relation between the firing angle of SCR and the output?
a) Directly proportional to each other
b) Inversely proportional to each other
c) Independent of each other
d) Both are zero

Explanation: The relation between the firing angle of SCR and the output is that they are inversely proportional to each other. The output of the SCR decreases when the firing angle is increased and vice versa.

6. Gate loses control when the SCR starts conducting.
a) True
b) False

Explanation: Gate loses control when the SCR starts conducting. The SCR is controlled through the gate. Once the SCR is triggered, the gate loses control over it. The gate is only used to trigger the device.

7. What is the use of Fast acting current limiting fuses?
a) To protect SCR from over current
b) To turn on SCR
c) To increase the flow of current
d) To stop the current

Explanation: The fast acting current limiting fuses are used to limit the value of the current and thus they are used to protect the SCR from over current and surge currents. The other options are not accurate answers.

8. What are the main components used in a snubber circuit?
a) Resistors
b) Capacitors
c) Transistors
d) Resistors and Capacitors

Explanation: The main components used in a snubber circuit are resistors and capacitors. They are generally used to suppress the voltage spikes. In most of the snubber circuits, the resistors and the capacitors are connected in series.

9. An SCR is a ____
a) N-P-N device
b) N-P-N-P device
c) P-N-P-N device
d) P-N-P device

Explanation: An SCR is a P-N-P-N type device. The layers are the p-n-p-n layer and there are three p-n junctions. There are three terminals named as anode, cathode and the gate terminal. The other options mentioned above are incorrect.

10. Which among the following are not the parts of SCR?
a) Anode
b) Cathode
c) Gate
d) Base

Explanation: An SCR has three terminals anode, cathode and gate. It does not consist of a base. It has four layers and three junctions. As the conduction takes place only in a single direction, an SCR is a unidirectional device.

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