1. What is the order of magnitude of the response time of LED?
a) 10-6
b) 10-9
c) 10-15
d) 10-3
Explanation: The response time of a LED is typically in the order of nanoseconds.
2. Which of the following is not an advantage of using a LED?
a) High response time
b) Compatibility with solid-state circuits
c) Rugged construction and high lifetime
d) No need for a heat sink in long run
Explanation: The response time of a LED is typically in the order of nanoseconds. The operating voltage range for LED is between 1.7 V to 3.3 V which makes it compatible with solid-state circuits. Also, the semiconductor construction makes them rugged. However, in the long run, an adequate heat sink is required for longevity
3. A LED will glow if connected under reverse bias configuration.
a) True
b) False
Explanation: A Light Emitting Diode works just like any other diode and hence it does not conduct under reverse bias operation and hence the LED will not glow.
4. An active device is one which ___________
a) Mechanically controls electron flow
b) Electrically controls electron flow
c) Pneumatically controls electron flow
d) Automatically controls electron flow
Explanation: An active device is any type of circuit component with the ability to electrically control electron flow (electricity controlling electricity). For a circuit to be properly called electronic, it must contain at least one active device.
5. Which of the following elements comprise of the passive devices?
a) Resistors, Capacitors and SCRs
b) Vacuum Tubes, SCRs and Diodes
c) Transformers, Inductors and Diodes
d) Transformers, TRIACs and DIACs
Explanation: A passive device is any type of circuit component which cannot control the flow of electrons by means of any electric control. All these devices do not have the ability to electrically control the flow of electrons.
6. A transistor is a current controlled device because_______________
a) In the base region movement of charge carrier is because of the electrons which are minority charge carrier in the base region
b) In the collector region movement of charge carrier is because of the electrons which are minority charge carrier in the collector region
c) In the base region movement of charge carrier is because of the holes which are majority charge carrier in the base region
d) In the collector region movement of charge carrier is because of the holes which are majority charge carrier in the base region
Explanation: In the base region movement of charge carrier is because of the electrons which is minority charge carrier in the base region. So, a BJT can said to be minority current controlled device. Base current flows between base and emitter in the BJT to induce a larger current flow between emitter and collector.
7. Active devices can also be used as_________
a) Amplifiers
b) Choppers
c) Converters
d) Inverters
Explanation: Active devices may be employed to a govern large amount of power by application of small amount of power. This behaviour is known as amplification. Therefore, active devices can be used as amplifiers.
8. How do amplifiers work without violating Law of Conservation of Energy?
a) They amplify one factor of the input and reduce others
b) They work on the law of conservation of mass
c) They violate the Law of Conservation of Energy
d) They amplify the signal by taking an input from an external source
Explanation: The Law of Conservation of Energy is not violated because the additional power is supplied by an external source, usually a DC battery or equivalent. The amplifier neither creates nor destroys energy, but merely reshapes it into the waveform desired.
9. The overall gain of multiple amplifiers in cascade can be expressed as__________ (A1, A2, A3 are individual gains)
a) A1-A2-A3
b) A1+A2+A3
c) A1/A2*A3
d) A1*A2*A3
Explanation: Gain can be voltage, current or power. Thus, when we put multiple stages in cascade the total gain will be the product of gains at individual stages. This is because the gain in successive stages increases greatly because of multiplication.
10. To overcome the problem of representation of large values of gain, which of the following units was introduced?
a) Decibels
b) Joules
c) Pascals
d) Farads
Explanation: Since 1dB=(1/10)log10(A2/A1) it is a logarithmic scale of representation and very large values can be expressed by smaller numbers. Decibels is a convenient unit of measurement for a variety of applications.