To solve this problem, let's explore the concept of systematic errors in measurements and the factors that contribute to them.
Systematic errors are reproducible inaccuracies that occur in the measurement process. Unlike random errors, which fluctuate unpredictably, systematic errors consistently affect measurements in the same way each time. These errors often stem from imperfections or biases in the measurement system or instrument.
Systematic errors can occur due to a variety of factors, including:
- Option 1: "Accuracy in the measurement" – This is incorrect. Accuracy refers to how close a measurement is to the true value. While systematic errors affect accuracy, the presence of systematic errors is not due to a lack of accuracy. Accuracy is the result of minimizing errors.
- Option 2: "Significant digits in the measurement" – This is incorrect. Significant digits refer to the precision with which a measurement is expressed. While significant digits affect the representation of data, they do not directly lead to systematic errors. Systematic errors result from factors such as calibration or environmental influences, not the number of significant digits used.
- Option 3: "Precision in the measurement" – This is incorrect. Precision refers to how consistently measurements can be repeated. Systematic errors are not caused by a lack of precision. In fact, measurements can be highly precise (i.e., consistent) but still inaccurate due to systematic errors.
- Option 4: "Gradation of the instrument" – This is correct. The gradation of the instrument refers to the smallest divisions or markings on the measuring scale. If the gradation is incorrect or poorly defined, it can lead to systematic errors. For example, a miscalibrated instrument with poorly defined gradations may consistently over- or under-read values, leading to systematic errors in all measurements.
Understanding the sources of systematic errors is essential for improving measurement accuracy. Systematic errors are typically more predictable than random errors and can often be corrected by calibrating instruments, improving measurement procedures, or adjusting for environmental factors. Identifying and minimizing systematic errors ensures that measurements reflect true values as closely as possible.
The correct answer is "Gradation of the instrument."
Consider the unity-negative-feedback system shown in Figure (i) below, where gain \( K \geq 0 \). The root locus of this system is shown in Figure (ii) below.
For what value(s) of \( K \) will the system in Figure (i) have a pole at \( -1 + j1 \)?

Consider a message signal \( m(t) \) which is bandlimited to \( [-W, W] \), where \( W \) is in Hz. Consider the following two modulation schemes for the message signal:
• Double sideband-suppressed carrier (DSB-SC): \[ f_{DSB}(t) = A_c m(t) \cos(2\pi f_c t) \] • Amplitude modulation (AM): \[ f_{AM}(t) = A_c \left( 1 + \mu m(t) \right) \cos(2\pi f_c t) \] Here, \( A_c \) and \( f_c \) are the amplitude and frequency (in Hz) of the carrier, respectively. In the case of AM, \( \mu \) denotes the modulation index. Consider the following statements:
(i) An envelope detector can be used for demodulation in the DSB-SC scheme if \( m(t)>0 \) for all \( t \).
(ii) An envelope detector can be used for demodulation in the AM scheme only if \( m(t)>0 \) for all \( t \).
Which of the following options is/are correct?
A controller \( D(s) \) of the form \( (1 + K_D s) \) is to be designed for the plant \[ G(s) = \frac{1000\sqrt{2}}{s(s+10)^2} \] as shown in the figure. The value of \( K_D \) that yields a phase margin of \(45^\circ\) at the gain cross-over frequency of 10 rad/sec is _____________ (round off to one decimal place). 