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# Multiple choice question for engineering

## Set 1

1. The voltage equivalent of temperature (Vt) in a P-N junctions is given by.
a) T/1000 volts
b) T/300 volts
c) T/1600 volts
d) T/11600 volts

Answer: d [Reason:] We know that the P-N junction is temperature dependent, it varies with the change in temperature the measure of change that is the voltage equivalent of temperature is given by Vt = T/11600 volts.

2. At room temperature what will be voltage equivalent of temperature.
a) 10 mV
b) 4.576 mV
c) 26 mV
d) 98 V

Answer: c [Reason:] Room temperature is 27o C = 300 k .We know that Vt= T/11600 volts by substituting the value of T we get 300/11600 = 26mV.

3. In a P-N junction the positive voltage at which the diode starts to conduct consequently is called.
a) Cut off voltage
b) Saturation voltage
c) Knee voltage
d) Breakdown voltage

Answer: c [Reason:] At a certain critical voltage, a large reverse current flows and the diode is said to be in breakdown region, at this region the diode will be forward biased and starts to conduct consequently.

4. In volt ampere characteristics the current increases with voltage _________
a) Exponentially
b) Equally
c) Sinusoidal
d) Unequally

Answer: a [Reason:] The current in the volt ampere characteristics increases exponentially with respect to voltage I(t) = eV(t).

5. The cut off voltage for diode of silicon semiconductor and germanium semiconductor is ____ volts.
a) 0.5 and 0.1
b) 0.7 and 0.3
c) 1 and 0.5
d) 0.5 and 1

Answer: b [Reason:] The cut off voltage is the voltage only after which the semiconductors conduct, the cut off voltage for silicon is 0.7V in the sense the silicon diode will conduct only when voltage is more than 0.7V and 0.3 for germanium.

6. What would be the current and voltage when there is no external voltage applied on the diode?
a) 0
b) 0.7
c) 0.3
d) 1

Answer: a [Reason:] When there is no external voltage applied on the circuit it acts as an open circuit and there will be no flow of charges hence the current and voltage will be zero.

7. In P-N junction V-I characteristics during forward biased, at what region the current increase is very low.
a) Saturation
b) Depletion
c) Cut off
d) Breakdown

Answer: b [Reason:] In the V-I characteristics the change in the current with respect to voltage is very less in depletion region due to the large resistance in the circuit as the resistance deceases by a certain value the current increases exponentially with voltage.

8. In a P-N junction diode during forward bias if the current increases more than the value that is rated will destroy the diode.
a) True
b) False

Answer: a [Reason:] If the current in the P-N junction diode during forward bias increases beyond the value rated on it will destroy the diode because voltage is directly proportional to current so extreme voltage will burn the diode down.

9. When the P-N junction diode is forward bias the current in circuit is controlled by.
a) External voltage
b) Capacitance
c) Resistance
d) Internal voltage

Answer: c [Reason:] When the P-N junction is in forward bias that is the p side connected to the positive terminal of voltage source the current in the circuit can be varied by varying the resistance, the current flow decreases as the resistance increases and vice versa.

10. The P-N junction diode conducts in which direction.
a) Reverse direction
b) Forward direction
c) Both Forward and Reverse direction
d) Neither Forward nor Reverse direction

Answer: b [Reason:] The P-N junction diode conducts only in forward direction, it will not conduct in reverse direction so only Zener Diode was introduced as it conducts in both forward and reverse direction.

## Set 2

1. Zener diodes are also known as
a) Voltage regulators
b) Forward bias diode
c) Breakdown diode
d) None of the mentioned

Answer: c [Reason:] Zener diodes are used as voltage regulators but they aren’t called voltage regulators. They are called breakdown diodes since they operate in breakdown region.

2. Which of the following is true about the resistance of a Zener diode?
a) It has an incremental resistance
b) It has dynamic resistance
c) The value of the resistance is the inverse of the slope of the i-v characteristics of the Zener diode
d) All of the mentioned

Answer: d [Reason:] All of the statements are true for the resistance of the zener diode.

3. Which of the following is true about the temperature coefficient or TC of the Zener diode?
a) For Zener voltage less than 5V, TC is negative
b) For Zener voltage around 5V, TC can be made zero
c) For higher values of Zener voltage, TC is positive
d) All of the mentioned

Answer: d [Reason:] All of the mentioned are true for the TC of a zener diode.

4. Which of the following can be used in series with a Zener diode so that combination has almost zero temperature coefficient?
a) Diode
b) Resistor
c) Transistor
d) MOSFET

Answer: a [Reason:] If a Zener diode of TC of about -2mV is connected with a forward diode (which has a TC of about +2mV) in series, the combination can be used to obtain a very low (close to zero) TC.

5. In Zener diode, for currents greater than the knee current, the v-i curve is almost
a) Almost a straight line parallel to y-axis
b) Almost a straight line parallel to x-axis
c) Equally inclined to both the axes with a positive slope
d) Equally inclined to both the axes with a negative slope

Answer: b [Reason:] Note that the curve is v-I curve and not an i-v curve.

6. Zener diodes can be effectively used in voltage regulator. However, they are these days being replaced by more efficient
a) Operational Amplifier
b) MOSFET
c) Integrated Circuits
d) None of the mentioned

Answer: c [Reason:] ICs have been widely adapted by the industries over conventional zener diodes as their better replacements for a voltage regulators.

7. A 9.1-V zener diode exhibits its nominal voltage at a test current of 28 mA. At this current the incremental resistance is specified as 5 Ω. Find VZ0 of the Zener model.
a) 8.96V
b) 9.03V
c) 9.17V
d) 9.24V

Answer: b [Reason:] VZ = VZo + MZ IZT 9.1 = VZo + 5 * 28 * 10-3 VZo = 8.96v VZ = VZo + 5IZ = 8.96 * 5IZ.

8. A shunt regulator utilizing a zener diode with an incremental resistance of 5 Ω is fed through an 82-Ω resistor. If the raw supply changes by 1.0 V, what is the corresponding change in the regulated output voltage?
a) 72.7 mV
b) 73.7 mV
c) 74.7 mV
d) 75.7 mV

9. A designer requires a shunt regulator of approximately 20 V. Two kinds of Zener diodes are available: 6.8-V devices with rz of 10 Ω and 5.1-V devices with rz of 30 Ω. For the two major choices possible, find the load regulation. In this calculation neglect the effect of the regulator resistance R.
a) -30mV/mA and 120mV/mA respectively
b) 30mV/mA and 60mV/mA respectively
c) -60mV/mA and +60mV/mA respectively
d) -30mV/mA and -120mV/mA respectively

Answer: d [Reason:] Three 6.8v zeners provide 3*6.8 = 20.4v with 3 * 10 =30Ω Resistance, neglecting R, we have load Regulation = -30mV/mA. For 5.1 Zeners we need 4 diodes to provide 20.4v with 4 * 30 =120Ω Resistance. load Regulation = -120mV/mA .

10. Partial specifications of a Zener diode is provided. VZ = 10.0 V, VZK = 9.6 V, and IZT = 50 mA. Assuming that the power rating of a breakdown diode is established at about twice the specified Zener current (IZT), what is the power rating of each of the diodes described above?
a) 1.04 W
b) 0.104 W
c) 10.4 mW
d) 1.04 mW

## Set 3

1. Which of the following circuits can be used as limiter or clamper or both?
a)
b)
c)
d) All of the mentioned

Answer: d [Reason:] Each of the circuit can be either as a clamper or limiter or both.

2. The V0 vs VI curve for the below circuit is

a)
b)
c)
d)

Answer: d [Reason:] Only this curve represents the characteristics correctly.

3. For the circuit and the input signal shown which of the following is true for the output voltage?

a) The output waveform is a square wave with lowest peak clamped to 0V
b) The output wave is a square wave with lowest peak clamped to -6V
c) The output waveform is a square wave with highest peak clamped to 4V
d) The output waveform is a straight line with the value of output voltage equal to 10V

Answer: a [Reason:] It is a clamped capacitor circuit.

4. Which of the following is not true for the duty cycle of a waveform?
a) Duty cycles can be used to describe the percent time of an active signal in an electrical device
b) Duty cycle can be used to determine the percentage of the time a signal is active
c) 60% duty cycle means that the waveform is active for 40% of the total time
d) 50% duty cycle means that the waveform is non-active for 50% of the total time

Answer: c [Reason:] 60% duty time means that a signal is active for 60% of the total time.

5. The maximum and the minimum voltage across the diode D1 respectively is

a) 2Vp and 0V respectively
b) 0V and -2Vp respectively
c) Vp and -Vp respectively
d) 2Vp and Vp respectively

Answer: b [Reason:] It is a voltage doubler circuit.

6. Limiting and clamping circuits are employed in
a) FM transmitters
c) Production of various signal waveforms such as trapezoidal, square or rectangular waves
d) All of the mentioned

Answer: d [Reason:] All of the given are uses of limiting and clamping circuits.

7. Which of the following is not true for a Schottky-Barrier Diode (SBD)?
a) It is formed by bringing metal into contact with a moderately doped n-type semiconductor material.
b) In the SBD, current is conducted by mainly by minority carriers.
c) The forward voltage drop of a conducting SBD is lower than that of a pn-junction diode.
d) SBD are used in the design of a special form of bipolar-transistor logic circuits

Answer: d [Reason:] Current is conducted largely by electrons which are majority current carriers.

8. Photodiodes are part of
a) Optoelectronics
b) High Intensity Discharge
c) Low pressure Discharge
d) None of the mentioned

Answer: a [Reason:] Optoelectronics are also called photodiodes.

9. Which of the following is true for LEDs
a) The light emitted by a LED is inversely proportional to the current flowing through the diode
b) LED operate in a manner opposite to the working of the optoelectronics or photodiodes
c) LED cannot be used to generate coherent source of light
d) None of the mentioned

Answer: b [Reason:] The working of the optoelectronics is opposite to that of the LEDs.

10. Optoisolator is
a) A combination of LED and varactor in the same package
b) A combination of a varactor and photodiode in the same package
c) A combination of LED and a photodiode in the same package
d) A combination of photodiode and Schottky-Barrier Diode in the same package

Answer: c [Reason:] By definition, an optoisolator is a package containing both LED as well as a photodiode.

## Set 4

1. In chain dimension, the dimensions are arranged parallel to each other.
a) True
b) False

Answer: b [Reason:] In chain dimension, the dimensions are arranged in a straight line. The type of dimensioning in which the dimensions are arranged parallel to each other is called as Parallel Dimension. The combination of both the type is called as combined dimension.

2. In combined dimension, the dimensions are arranged in a straight line only.
a) True
b) False

Answer: b [Reason:] In combined type of dimension, the dimensions are arranged in a straight line as well as parallel to each other. It depends on the convenience of dimensioning and the important dimensions. When more than two dimensions overlap, combined dimensioning is done.

3. In which of the following type of dimensioning, the dimensions are arranged only in a straight line?
a) Parallel dimension
b) Chain Dimension
c) Combined dimension
d) Aligned dimension

Answer: b [Reason:] In chain dimension, the dimensions are arranged only in a straight line. In this type of dimensioning, the dimensions appear less crowded and make it easier to read. There is almost less confusion while interpreting the dimensions.

4. Which type of dimensioning is shown in the figure?

a) Parallel dimension
b) Unidirectional dimension
c) Combined dimension
d) Chain Dimension

Answer: a [Reason:] The dimensions are arranged in a parallel manner. Hence the answer is parallel dimension. This type of dimensioning is also called as aligned dimension, as the dimension figures are aligned along the length of the dimension line.

5. Which type of dimensioning is shown below?

a) Chain dimension
b) Parallel dimension
c) Unidirectional dimension
d) Combined dimension

Answer: a [Reason:] The type of dimensioning followed is chain dimension. The dimensions are arranged in a straight line. In this example, the aligned dimensioning system is being used i.e. the dimension figures are aligned along the length of the dimension line.

6. Which type of dimensioning is done below?

a) Unidirectional and chain dimension
b) Aligned and parallel dimension
c) Aligned and chain dimension
d) Unidirectional and parallel dimension

Answer: a [Reason:] The dimension figures are written in such a way that they can be read from bottom only. The chain dimensioning is used as the dimensions are arranged in a straight line. In parallel dimension, the dimension lines are arranged parallel to each other.

7. Identify the type of dimensioning used in the figure below.

a) Parallel and aligned dimension
b) Parallel and unidirectional dimension
c) Chain and aligned dimension
d) Chain and unidirectional dimension

Answer: c [Reason:] The type of dimensioning done is chain and aligned dimension. The dimensions are arranged in a straight line and the dimension figures are aligned along the length of the dimension line. The dimension figures can be read from the right side as well as bottom.

8. Identify the type of dimensioning used in the example below.

a) Parallel and aligned dimension
b) Chain and aligned dimension
c) Chain and unidirectional dimension
d) Combined and aligned dimension

Answer: d [Reason:] The type of dimensioning done is combined dimensioning and the system of dimensioning used is aligned. The dimensions are arranged in both ways i.e. parallel as well as in a straight line. The dimension figures are aligned along the length of the dimension line.

9. Which type of dimensioning is done in the example below?

a) Parallel dimension
b) Chain dimension
c) Combined dimension
d) Aligned dimension

Answer: c [Reason:] The dimensions are arranged parallel to each other in horizontal dimensioning and in straight line for vertical dimensioning. There is a need for calculation for finding out some dimensions. The dimension figures can be read only from the bottom.

10. Identify the type and system of dimensioning in the example given below.

a) Unidirectional and parallel dimension
b) Unidirectional and chain dimension
c) Unidirectional and combined dimension
d) Aligned and combined dimension

Answer: c [Reason:] The example has unidirectional and chain type of dimensioning. The dimension figures are arranged horizontally and can only be read from the bottom. The dimensions are arranged in a straight line and not in parallel direction.

## Set 5

1. Which of the following dimension is according to the ‘aligned system’ of dimensioning?

a) 40
b) 55
c) 25
d) 10

Answer: a [Reason:] In aligned system of dimensioning, the dimensions are written on the dimension line. Their alignment is along the length of the dimension line. The dimensions are always written either on top or below the dimension line but never cutting it.

2. In dimensioning, the lines enclosing the dimension line are known as ____
b) Dimension line
c) Extension line
d) Outline

Answer: c [Reason:] The extension line encloses the dimension line. It starts and ends with the line to be dimensioned. The extension line is extended beyond the dimension line by 4mm. It helps in defining proper boundaries for the dimension line.

3. When dimensioning the circle, the dimension line begins from the centre of the circle.
a) True
b) False

Answer: a [Reason:] When dimensioning the circle, the dimension line begins from the centre of the circle. With the help of the leader line, the dimensions are written on it. The notations φ and R are used to indicate whether the dimension denotes diameter or the radius respectively.

4. While dimensioning a circle, the leader line and the dimension line are drawn at which angle with respect to each other?
a) 45˚
b) 30˚
c) 0˚ or 180˚
d) 90˚

Answer: c [Reason:] When dimensioning a circle, the leader line and the dimension line are drawn 0˚ or 180˚ with respect to each other. This helps in clear dimensioning of the circle. It also reduces the difficulty in reading the dimensions when there are concentric circles involved.

5. While dimensioning holes, slots, etc. how would their number be specified?
a) Number written on the dimension line
b) Number is written of the leader line
c) Number is written on the corner of the page
d) Number is written on the side of the hole or slot.

Answer: a [Reason:] The number of holes, slots, etc. is written on the dimension line along with the dimensions. For example, if there are four holes of same dimensions; then only one of the holes will have their dimensions specified and along with dimensions, the number is also written; 4Holes, φx mm.

6. What is the height if the dimension figures written on the dimension line?
a) 7mm to 9mm
b) 2mm to 3mm
c) 6mm to 8mm
d) 3mm to 5mm

Answer: d [Reason:] It is customary to write the figures with a height of 3mm to 5mm. This helps in the readability of the dimension figures. It also makes reading the dimensions easy. The thickness of the letters is so adjusted that it can read without effort.

7. While dimensioning, what should always be written before a point accompanied by a figure if the value of the figure is less than unity?
a) 1
b) 0
c) 2
d) 6

Answer: b [Reason:] For figures having value less than one, dimensions should be written as 0.5 or 0.3 as per the value. There needs to be a zero in front of the point if it is less than 1. Sometimes zero is omitted but this practice should not be encouraged.

8. In unidirectional system, the figures are written along the dimension line.
a) True
b) False