Analog And Digital Electronics
Questions and Answers
- 1.
The majority carriers in the emitter of a PNP transistors are
- A.
Holes
- B.
Free electrons
- C.
Trivalent atoms
- D.
Pentavalent atoms
Correct Answer
A. HolesExplanation
In a PNP transistor, the majority carriers in the emitter are holes. This is because in a PNP transistor, the emitter is made up of p-type material, which has an excess of holes (positive charge carriers). When a positive voltage is applied to the base, it attracts these holes towards it, allowing them to flow from the emitter to the base. Therefore, the majority carriers in the emitter of a PNP transistor are holes.Rate this question:
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- 2.
A LED produces light when-
- A.
Unbiased
- B.
Reverse biased
- C.
Foreward biased
- D.
None of the above
Correct Answer
C. Foreward biasedExplanation
When a LED is forward biased, it means that the positive terminal of the power source is connected to the anode of the LED, and the negative terminal is connected to the cathode. In this configuration, the LED allows current to flow through it, and as a result, it emits light. This is because forward biasing creates a forward voltage across the LED, which causes the electrons and holes in the semiconductor material to recombine and release energy in the form of light.Rate this question:
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- 3.
A 2 transistor class B power amplifier is commonly called-
- A.
Push-pull
- B.
Dual
- C.
Differential
- D.
None of these
Correct Answer
A. Push-pullExplanation
A 2 transistor class B power amplifier is commonly called "push-pull" because it consists of two transistors that work together in a complementary manner to amplify the input signal. In a push-pull configuration, one transistor conducts during the positive half of the input signal while the other conducts during the negative half. This arrangement allows for efficient amplification and reduces distortion in the output signal. The term "push-pull" refers to the push and pull action of the transistors in amplifying the signal.Rate this question:
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- 4.
Negative feedback is an amplifier is -
- A.
Reduced gain
- B.
Increased noise
- C.
Increased frequency and phase
- D.
Reduced bandwidth
Correct Answer
A. Reduced gainExplanation
Negative feedback is an amplifier is reduced gain. This means that the overall amplification of the system is decreased. Negative feedback is a technique used in amplifiers to reduce distortion and improve stability by feeding a portion of the output signal back to the input in opposite phase. This helps to counteract any fluctuations or variations in the input signal, resulting in a more accurate and controlled output. However, this feedback also reduces the overall gain of the amplifier, as it opposes the original amplification.Rate this question:
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- 5.
Maximum efficiency of transformer coupled class A power amplifier is-
- A.
78.50%
- B.
50%
- C.
25%
- D.
100%
Correct Answer
B. 50%Explanation
The maximum efficiency of a transformer coupled class A power amplifier is 50%. This means that only half of the input power is converted into output power, while the other half is dissipated as heat. Class A amplifiers are known for their high linearity and low distortion, but they are not very efficient due to the constant current flow through the output transistors, even when there is no input signal. Therefore, only 50% of the input power is effectively utilized to produce the desired output power.Rate this question:
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- 6.
The maximum efficiency of a push pull class B power amplifier is-
- A.
78.50%
- B.
50%
- C.
25%
- D.
None of these
Correct Answer
A. 78.50%Explanation
The maximum efficiency of a push-pull class B power amplifier is 78.50%. This means that the amplifier is able to convert 78.50% of the input power into output power, while the remaining 21.50% is lost as heat or dissipated in the circuit. Push-pull amplifiers are designed to minimize distortion and improve efficiency by using two complementary transistors that work in opposite phases. This configuration allows for better power handling and reduced power dissipation compared to single-ended amplifiers. Therefore, the correct answer is 78.50%.Rate this question:
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- 7.
A CE Transistor power amplifier operates with quiescent values of Vcq= 6V and Icq=50mA. The output signal voltage varies from 1 to 11V and the output current varies from 10 to 90 mA. Find the DC input power to the transistor-
- A.
0.3W
- B.
0.5W
- C.
1W
- D.
None of these
Correct Answer
A. 0.3WExplanation
The DC input power to the transistor can be calculated by multiplying the quiescent values of voltage and current. In this case, Vcq is given as 6V and Icq is given as 50mA. Therefore, the DC input power is calculated as 6V * 50mA = 0.3W.Rate this question:
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- 8.
A CE Transistor power amplifier operates with quiescent values of Vcq= 6V and Icq=50mA. The output signal voltage varies from 1 to 11V and the output current varies from 10 to 90 mA. Find the AC output power-
- A.
0.1W
- B.
0.3W
- C.
0.5W
- D.
None of these
Correct Answer
A. 0.1WExplanation
The AC output power can be calculated using the formula P = V * I, where P is the power, V is the voltage, and I is the current. In this case, the minimum voltage is 1V and the maximum voltage is 11V, while the minimum current is 10mA and the maximum current is 90mA.
Using the minimum values, the power would be 1V * 10mA = 0.01W.
Using the maximum values, the power would be 11V * 90mA = 0.99W.
Since the AC output power varies between 0.01W and 0.99W, none of the given options (0.1W, 0.3W, 0.5W) is correct.Rate this question:
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- 9.
A CE Transistor power amplifier operates with quiescent values of Vcq= 6V and Icq=50mA. The output signal voltage varies from 1 to 11V and the output current varies from 10 to 90 mA. Find the efficiency-
- A.
33.30%
- B.
35%
- C.
25%
- D.
50%
Correct Answer
A. 33.30%Explanation
The efficiency of a power amplifier is defined as the ratio of the output power to the input power. In this case, the output power can be calculated by multiplying the peak output voltage (11V) by the peak output current (90mA), while the input power can be calculated by multiplying the quiescent voltage (6V) by the quiescent current (50mA). Dividing the output power by the input power and multiplying by 100 gives the efficiency as a percentage. In this case, the efficiency is calculated to be 33.30%.Rate this question:
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- 10.
Audio frequency range-
- A.
20 Hz to 20 KHz
- B.
3 Hz to 30 KHz
- C.
50 MHz
- D.
None of the above
Correct Answer
A. 20 Hz to 20 KHzExplanation
The audio frequency range refers to the range of frequencies that can be heard by the human ear. The human ear is generally sensitive to frequencies between 20 Hz (low frequency) and 20 KHz (high frequency). Therefore, the correct answer is 20 Hz to 20 KHz as it represents the typical range of audible frequencies for humans.Rate this question:
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- 11.
The input resistance of an ideal voltage amplifier is
- A.
Infinity
- B.
Zero
- C.
Unity
- D.
None of the above
Correct Answer
A. InfinityExplanation
An ideal voltage amplifier has an input resistance of infinity because it draws no current from the source it is connected to. This means that the amplifier does not load the source and does not affect the source's output voltage. In practical terms, this means that the input resistance is so high that it can be considered infinite, ensuring that the voltage amplifier operates without any loss or distortion of the input signal.Rate this question:
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- 12.
The output resistance of an ideal voltage amplifier is
- A.
Infinity
- B.
Zero
- C.
Unity
- D.
None of the above
Correct Answer
B. ZeroExplanation
The output resistance of an ideal voltage amplifier is zero because an ideal voltage amplifier is assumed to have no internal resistance. Therefore, it can provide an output voltage without any drop in voltage due to resistance. This implies that the output voltage remains constant regardless of the load connected to the amplifier.Rate this question:
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- 13.
The input resistance of an ideal current amplifier is
- A.
Infinity
- B.
Zero
- C.
Unity
- D.
None of the above
Correct Answer
B. ZeroExplanation
The correct answer is zero because an ideal current amplifier has zero input resistance. This means that it draws no current from the input source, resulting in an infinite input impedance. In other words, the input resistance is so high that it can be considered zero for practical purposes. Therefore, an ideal current amplifier does not load the input source and allows for accurate current measurement or amplification.Rate this question:
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- 14.
The output resistance of an ideal current amplifier is
- A.
Infinity
- B.
Zero
- C.
Unity
- D.
None of the above
Correct Answer
A. InfinityExplanation
An ideal current amplifier has an output resistance of infinity because it is designed to provide a constant current regardless of the load impedance. This means that the output current remains unchanged even when the load impedance changes. An infinite output resistance ensures that the amplifier can deliver the desired current without any loss or distortion caused by the load impedance.Rate this question:
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- 15.
To work as a linear amplifier, a transistor must operate in-
- A.
The active region
- B.
The saturation region
- C.
Cut off region
- D.
None of these
Correct Answer
A. The active regionExplanation
A transistor must operate in the active region to work as a linear amplifier. In this region, the transistor is biased such that it is partially conducting, allowing it to amplify the input signal without distortion. The active region provides the necessary linear response for the transistor to accurately amplify the input signal. The saturation region and cut off region are not suitable for linear amplification as they result in distortion and limited amplification respectively. Therefore, the active region is the correct choice for a transistor to function as a linear amplifier.Rate this question:
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- 16.
Feedback always increases the gain of an amplifier.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Feedback does not always increase the gain of an amplifier. In some cases, feedback can actually decrease the gain of an amplifier. The purpose of feedback in an amplifier is to stabilize the output and reduce distortion, not necessarily to increase the gain. Depending on the design and configuration of the amplifier, feedback can have different effects on the gain. Therefore, the statement that feedback always increases the gain of an amplifier is false.Rate this question:
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- 17.
(21.625)10 = ( ) 2 ?
- A.
10001.001
- B.
10000.1
- C.
10101.101
- D.
10011.111
Correct Answer
C. 10101.101Explanation
To convert a decimal number to binary, we can repeatedly divide the decimal number by 2 and keep track of the remainders. Starting from the decimal point, the remainders form the binary representation of the number. In this case, starting with the integer part of 21.625 (21), we divide it by 2 to get a quotient of 10 and a remainder of 1. We continue this process with the quotient until we reach 0. For the fractional part of 0.625, we multiply it by 2 to get a product of 1.25. We take the integer part (1) as the first digit after the decimal point. We repeat this process with the fractional part until we reach the desired precision. Therefore, the binary representation of 21.625 is 10101.101.Rate this question:
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- 18.
(101111.11) 2 = ( ) 10 ?
- A.
52.85
- B.
49.75
- C.
42.25
- D.
47.75
Correct Answer
D. 47.75Explanation
The given question is asking for the decimal equivalent of the binary number (101111.11)2. To convert a binary number to decimal, we need to multiply each digit by the corresponding power of 2 and sum them up. In this case, the binary number can be broken down as follows: 1*2^5 + 0*2^4 + 1*2^3 + 1*2^2 + 1*2^1 + 1*2^0 + 1*2^-1 + 1*2^-2. Simplifying this expression gives us 32 + 0 + 8 + 4 + 2 + 1 + 0.5 + 0.25, which equals 47.75. Therefore, the correct answer is 47.75.Rate this question:
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- 19.
(125.201) 10 = ( ) 8 ?
- A.
178.52892
- B.
175.14672
- C.
176.11992
- D.
174.25922
Correct Answer
B. 175.14672Explanation
The given question asks for the equivalent of the number 125.201 in base 8. To convert a number from base 10 to base 8, we need to divide the number by 8 repeatedly and record the remainders in reverse order. The process reveals that 125.201 in base 10 is equivalent to 175.14672 in base 8.Rate this question:
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- 20.
(125.201) 10 = ( ) 16 ?
- A.
7D.3374B
- B.
7A.1052B
- C.
7B.0704C
- D.
7C.3387A
Correct Answer
A. 7D.3374BExplanation
The given question is asking for the decimal number 125.201 to be converted to its equivalent hexadecimal number. The correct answer is 7D.3374B.Rate this question:
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- 21.
How many binary digits are required to count to 10010?
- A.
7
- B.
2
- C.
3
- D.
100
Correct Answer
A. 7Explanation
To count to 10010 in binary, we need to determine the number of binary digits required. The binary number system uses only two digits, 0 and 1. To count up to 10010, we need to find the highest power of 2 that is less than or equal to 10010. In this case, the highest power of 2 that is less than or equal to 10010 is 2^13, which is equal to 8192. Therefore, we need 13 binary digits to represent 10010. However, since we only need to count up to 10010, we can discard the higher powers of 2. The next highest power of 2 is 2^12, which is equal to 4096. By subtracting 4096 from 10010, we get 5914. Now, we repeat the process and find that the highest power of 2 less than or equal to 5914 is 2^11, which is equal to 2048. By subtracting 2048 from 5914, we get 3866. We continue this process until we reach 10010. By doing this, we find that 7 binary digits are required to count to 10010.Rate this question:
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- 22.
The sum of 11101 + 10111 equals ________.
- A.
110011
- B.
100001
- C.
110100
- D.
100100
Correct Answer
C. 110100Explanation
The sum of 11101 + 10111 can be calculated by adding the corresponding digits from right to left. Starting from the rightmost digits, 1 + 1 equals 0 with a carry of 1. Moving to the second digits from the right, 0 + 1 + 1 equals 0 with a carry of 1. Continuing this process, 1 + 0 + 1 equals 0 with a carry of 1, and 1 + 1 + 0 equals 1 with no carry. Finally, adding the leftmost digit, 1 + 1 equals 0 with a carry of 1. Therefore, the sum is 110100.Rate this question:
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- 23.
A binary number's value changes most drastically when the ________ is changed.
- A.
MSB
- B.
Frequency
- C.
LSB
- D.
Duty cycle
Correct Answer
A. MSBExplanation
The most significant bit (MSB) of a binary number represents the highest value in the number. Changing the MSB from 0 to 1 or vice versa results in a significant change in the value of the binary number. This is because the MSB has the largest weight in determining the overall value of the number. Therefore, changing the MSB has the greatest impact on the value of a binary number.Rate this question:
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- 24.
The octal numbering system:
- A.
Simplifies tasks
- B.
Groups binary numbers in groups of 4
- C.
Saves time
- D.
Simplifies tasks and saves time
Correct Answer
D. Simplifies tasks and saves timeExplanation
The octal numbering system simplifies tasks and saves time because it allows for easier representation of binary numbers. By grouping binary numbers in groups of 4, the octal system provides a more compact and manageable way to express large binary numbers. This simplification and efficiency in representation can help in various tasks, such as computer programming and digital calculations, ultimately saving time and effort.Rate this question:
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- 25.
Hexadecimal letters A through F are used for decimal equivalent values from:
- A.
1 through 6
- B.
9 through 14
- C.
10 through 15
- D.
11 through 17
Correct Answer
C. 10 through 15Explanation
Hexadecimal is a number system that uses a base of 16, where the digits 0-9 represent their respective decimal values and the letters A-F represent decimal values 10-15. Therefore, the correct answer is 10 through 15, as these are the values assigned to the hexadecimal letters A-F.Rate this question:
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- 26.
Digital electronics is based on the ________ numbering system.
- A.
Decimal
- B.
Binary
- C.
Octal
- D.
Hexadecimal
Correct Answer
B. BinaryExplanation
Digital electronics is based on the binary numbering system because it uses only two digits, 0 and 1, to represent and manipulate information. In digital systems, binary digits, also known as bits, are used to represent the on/off states of electronic components, such as transistors. This binary representation allows for efficient and reliable storage, processing, and transmission of data in digital devices. Other numbering systems like decimal, octal, and hexadecimal are also used in certain applications, but binary is the fundamental system underlying digital electronics.Rate this question:
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- 27.
An informational signal that makes use of binary digits is considered to be:
- A.
Solid state
- B.
Digital
- C.
Analog
- D.
Nonoscillating
Correct Answer
B. DigitalExplanation
An informational signal that makes use of binary digits is considered to be digital. This is because digital signals are represented by a series of discrete values, typically 0s and 1s, which can be easily processed and transmitted by computers and other digital devices. Unlike analog signals, which are continuous and can have an infinite number of possible values, digital signals have a finite number of discrete states, making them more reliable and less susceptible to noise and interference. Therefore, the correct answer is digital.Rate this question:
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- 28.
When using the repeated division by 2 method of converting from decimal to binary, one must write the first remainder as the:
- A.
MSB
- B.
MSB, provided the following sequence of remainders are written in descending order until the final remainder is achieved.
- C.
LSB
- D.
LSB, provided the final remainder is used to replace the original LSB, which is then moved to the MSB position.
Correct Answer
A. MSBExplanation
In the repeated division by 2 method of converting from decimal to binary, the first remainder represents the Most Significant Bit (MSB) of the binary number. This is because the repeated division starts from the leftmost digit, which is the most significant digit in the binary representation. Therefore, the first remainder obtained will be written as the MSB.Rate this question:
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- 29.
The output of a logic gate is 1 when all its inputs are at logic 0. the gate is either
- A.
A NAND or an EX-OR
- B.
An OR or an EX-NOR
- C.
An AND or an EX-OR
- D.
A NOR or an EX-NOR
Correct Answer
D. A NOR or an EX-NORExplanation
A NOR gate is a logic gate that produces an output of 1 only when all its inputs are 0. This matches the given condition that the output is 1 when all inputs are at logic 0. An EX-NOR gate is a logic gate that produces an output of 1 when all its inputs are the same. Since the question states that all inputs are at logic 0, the inputs are the same, and therefore an EX-NOR gate can also satisfy the given condition.Rate this question:
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- 30.
The code where all successive numbers differ from their preceding number by single bit is
- A.
Binary code
- B.
BCD
- C.
Excess – 3
- D.
Gray
Correct Answer
D. GrayExplanation
Gray code is a binary numeral system where two successive values differ by only one bit. In Gray code, each binary number is assigned a unique representation such that only one bit changes at a time when moving from one number to the next. This property makes Gray code particularly useful in applications where minimizing errors during transitions is important, such as in analog-to-digital converters or rotary encoders. Therefore, Gray code is the correct answer for the code where all successive numbers differ from their preceding number by a single bit.Rate this question:
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- 31.
In a positive logic system, logic state 1 corresponds to
- A.
Positive voltage
- B.
Higher voltage level
- C.
Zero voltage level
- D.
Lower voltage level
Correct Answer
B. Higher voltage levelExplanation
In a positive logic system, logic state 1 corresponds to a higher voltage level. This means that when a signal is at logic state 1, it is represented by a higher voltage level compared to logic state 0. This convention is commonly used in digital systems where a higher voltage level represents an "on" or "true" state, while a lower voltage level represents an "off" or "false" state.Rate this question:
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- 32.
The result of adding hexadecimal number A6 to 3A is
- A.
DD
- B.
E0
- C.
F0
- D.
EF
Correct Answer
B. E0Explanation
When we add hexadecimal number A6 to 3A, we get the sum E0. In hexadecimal, A represents the value 10 and 6 represents the value 6. Similarly, 3 represents the value 3 and A represents the value 10. Adding these values together, we get 16 for the first digit, which is represented as E in hexadecimal. The second digit is 0, which is represented as 0 in hexadecimal. Therefore, the result of adding A6 to 3A is E0.Rate this question:
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- 33.
What does a decimal number represents?
- A.
Quality
- B.
Quantity
- C.
Position
- D.
None of these
Correct Answer
C. PositionExplanation
A decimal number represents position. In a decimal number, each digit's value is determined by its position relative to the decimal point. The position of a digit determines its place value, such as ones, tens, hundreds, etc. Therefore, the answer "Position" accurately describes what a decimal number represents.Rate this question:
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- 34.
A digit in base R will have a range from
- A.
1 to R-1
- B.
0 to R-1
- C.
1 to R+1
- D.
0 to R+1
Correct Answer
B. 0 to R-1Explanation
In base R, the range of a digit is from 0 to R-1. This is because in base R, the digits used are from 0 to R-1, where R represents the base. The digit 0 represents the lowest value and the digit R-1 represents the highest value in the base R system. Therefore, the range of a digit in base R is from 0 to R-1.Rate this question:
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- 35.
ASCII code is required for representing more than ________ characters
- A.
16
- B.
8
- C.
64
- D.
32
Correct Answer
C. 64Explanation
ASCII code is a character encoding standard that uses numeric codes to represent characters. It was originally designed to represent a maximum of 128 characters, including letters, numbers, and special symbols. However, as technology advanced, an extended version of ASCII called Extended ASCII was developed, which allowed for the representation of up to 256 characters. Therefore, to represent more than 256 characters, a larger character encoding standard like Unicode would be required. The given answer of 64 is incorrect as it does not align with the concept of ASCII code and its limitations.Rate this question:
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- 36.
What will be the result in BCD form if two binary numbers 599 and 984 are added ?
- A.
1583
- B.
8513
- C.
8421
- D.
None of these
Correct Answer
A. 1583Explanation
The result in BCD form if two binary numbers 599 and 984 are added is 1583.Rate this question:
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- 37.
The MSB of _____________ is same as the MSB of the corresponding Gray code
- A.
Alphanumeric code
- B.
Excess-3 code
- C.
Binary code
- D.
Gray code
Correct Answer
C. Binary codeExplanation
The MSB (Most Significant Bit) of the Binary code is the same as the MSB of the corresponding Gray code. This means that the leftmost bit of the Binary code and the leftmost bit of the Gray code will have the same value.Rate this question:
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- 38.
DeMorgan’s first theorem shows the equivalence of
- A.
OR gate and Exclusive OR gate
- B.
NOR gate and Bubbled AND gate
- C.
NAND gate and NOT gate
- D.
None of these
Correct Answer
B. NOR gate and Bubbled AND gateExplanation
DeMorgan's first theorem states that the complement of the logical OR operation between two variables is equivalent to the logical AND operation with the complement of each variable. In other words, the NOR gate is equivalent to a Bubbled AND gate, where the bubble represents the complement or negation of the output. This means that when the inputs to both gates are the same, their outputs will also be the same. Therefore, the correct answer is NOR gate and Bubbled AND gate.Rate this question:
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- 39.
(734)8 =(? )16
- A.
C 1 D
- B.
D C 1
- C.
1 C D
- D.
1 D C
Correct Answer
D. 1 D CExplanation
The given expression (734)8 can be converted to base 10 by multiplying each digit by the corresponding power of 8 and then summing them up. In this case, 7 * 8^2 + 3 * 8^1 + 4 * 8^0 = 448 + 24 + 4 = 476. To convert this decimal number to base 16, we divide it successively by 16 and record the remainders in reverse order. In this case, 476 / 16 = 29 with a remainder of 12 (C), 29 / 16 = 1 with a remainder of 13 (D), and 1 / 16 = 0 with a remainder of 1. Therefore, the base 16 representation of (734)8 is 1DC.Rate this question:
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- 40.
-8 is equal to signed binary number
- A.
10001000
- B.
11001000
- C.
10000000
- D.
11000000
Correct Answer
A. 10001000Explanation
The given binary number 10001000 represents the signed binary representation of -8. In signed binary representation, the leftmost bit is used to indicate the sign, with 0 representing positive and 1 representing negative. In this case, the leftmost bit is 1, indicating a negative number. The remaining bits, 0001000, represent the magnitude of the number, which is 8. Therefore, the binary number 10001000 represents -8 in signed binary form.Rate this question:
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