Ongc Graduate Trainee Exam 2012 Free Online Practice Test

The conductivity of intrinsic semiconductors depends on both temperature and band gap. Temperature affects the movement of charge carriers within the material, increasing conductivity as temperature increases. The band gap, on the other hand, determines the energy required for the charge carriers to move, affecting conductivity. Therefore, both factors play a role in determining the conductivity of intrinsic semiconductors.

The unity-gain frequency of an op-amp is the frequency at which the open-loop gain drops to 1. In this case, the open-loop upper cut-off frequency is given as 20 Hz. This means that the open-loop gain starts to decrease significantly above this frequency. Since the open-loop gain is given as 100000, it can be assumed that the gain is approximately constant up to the open-loop upper cut-off frequency. Therefore, the unity-gain frequency would be significantly higher than 20 Hz. Among the given options, the only frequency that is significantly higher than 20 Hz is 2 MHz, so it is the correct answer.

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The correct answer is 2 4 1 3. This means that the characteristics of the devices in List I match with the corresponding devices in List II as follows: MOSFET has high current gain, Zener diode provides voltage regulation, Tunnel diode has voltage controlled negative resistance, and BJT has high input impedance.

When the switch 'S' is closed, the circuit reaches a steady-state, meaning that the current in the inductor stabilizes. However, when the switch 'S' is opened, the circuit is disrupted and the current in the inductor will start to decrease. The rate at which the current decreases is determined by the time constant, which is a measure of how quickly the current decays. In this case, the time constant is 0.5s, indicating that the current in the inductor will decay exponentially with a time constant of 0.5s.

To avoid thermal runway in the design of an analog circuit, the operating point of the BJT should be such that VCE > 1/2VCC. This condition ensures that the voltage across the collector-emitter junction is greater than half of the supply voltage. If VCE is too low, it can lead to thermal runaway, where the temperature of the transistor increases rapidly, potentially causing damage. By maintaining VCE above half of VCC, the circuit can operate within safe temperature limits and prevent thermal runaway.

A 3½ digit voltmeter with a resolution of 100 mV means that it can display values up to 999.9V. Since the maximum voltage it can measure is 1000V, the correct answer is 100V.

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The gauge factor of a strain gauge is defined as the ratio of the change in resistance to the change in length of the element. This means that the gauge factor quantifies the sensitivity of the strain gauge to changes in length. As the length of the element changes due to applied force or strain, the resistance of the strain gauge also changes. The higher the gauge factor, the more sensitive the strain gauge is to these changes in length. Therefore, the correct answer is resistance to the per unit change in the length of the element.

A semiconductor with an energy gap of 1.1 eV would be opaque to visible light. This is because the energy gap determines the minimum energy required for an electron to transition from the valence band to the conduction band. In this case, the energy gap is large enough that visible light, which has lower energy, cannot provide the necessary energy for electrons to make this transition. As a result, the semiconductor would absorb visible light and appear opaque.

The correct sequence of these devices in increasing order of their input impedance is 1,2,3,4. The input impedance of a device refers to how much it resists the flow of current into its input terminal. In general, the input impedance of a BJT in CB mode is higher than that of a BJT in CE mode. JFETs typically have higher input impedance compared to BJTs. MOSFETs usually have the highest input impedance among the listed devices. Therefore, the correct sequence is 1,2,3,4.

The correct sequence for these converters in decreasing order of their speed is 3, 2, 1. The flash type converter is the fastest, followed by the counter type converter, and finally the dual slope type converter.

The electrical conductivity of metals is primarily due to the presence of free electrons, which can move easily through the material. As the temperature increases, the free electrons gain more thermal energy, leading to increased collisions with atoms and impurities in the material. These collisions impede the flow of electrons, resulting in a decrease in electrical conductivity.

On the other hand, intrinsic semiconductors have a small number of free electrons and holes at room temperature. As the temperature increases, more electrons are excited from the valence band to the conduction band, creating more free charge carriers and increasing the electrical conductivity of the material.

Therefore, with increasing temperature, the electrical conductivity would decrease in metals but increase in intrinsic semiconductors.

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In a semiconductor, the energy gap refers to the difference in energy levels between the valence band and the conduction band. When an electron in the valence band absorbs energy, it can move to the conduction band, creating a conducting state. The energy gap determines the minimum energy required for this transition.

In this case, the answer "Transparent to Longer Wavelengths and Opaque to Shorter Wavelengths" is correct because a semiconductor is transparent to longer wavelengths of light, which have lower energy, and opaque to shorter wavelengths of light, which have higher energy. This means that longer wavelength light can pass through the semiconductor, while shorter wavelength light is absorbed and cannot pass through.

The correct answer is 3 1 4 2. This means that the correct match between List I (Bridges) and List II (Parameters) is as follows:
- Schering Bridge (C) corresponds to Inductance (3)
- Anderson Bridge (A) corresponds to Low Resistance (1)
- Wheal stone Bridge (D) corresponds to Capacitance (4)
- Kelvin Bridge (B) corresponds to Medium Resistance (2)

The driving point impedance synthesis involves matching the impedance of a given network. In Cauer I, the series combination of L and C is in parallel, while in Cauer II, the parallel combination of L and C is in series. Foster I has L in series arms and C in shunt arms of a ladder, while Foster II has C in series arms and L in shunt arms of a ladder. Therefore, the correct answer is 1 2 3 4, as it matches the given network configurations with the corresponding forms.

The given correct answer is "R and C". This means that the network consists of resistors (R) and capacitors (C). The explanation for this answer is that the poles and zeros of a driving-point function of a network are simple and interlace on the jw axis. This characteristic is typically observed in networks that include resistors and capacitors. Therefore, the presence of both resistors and capacitors in the network suggests that they are the elements responsible for the interlacing poles and zeros.

A hot wire anemometer is a device specifically designed to measure gas velocities. It works by passing a current through a thin wire, which heats up due to the airflow. The rate at which the wire cools down is directly proportional to the gas velocity. By measuring the cooling rate, the hot wire anemometer can accurately determine the velocity of the gas. Therefore, the correct answer is gas velocities.

The correct answer is A is true but R is false. This means that Assertion A is true, which states that a circuit is in resonance if the voltage across the circuit is in phase with the current through it. However, Reason R is false, as the power factor of the circuit at resonance is not zero. The power factor at resonance depends on the type of reactance in the circuit.

The Anderson bridge is a modification of the Maxwell's inductance-capacitance bridge, making statement 1 correct. It is superior to the Maxwell's bridge for measuring the low Q of coils, which makes statement 2 correct. Additionally, it is simpler compared to the Maxwell's bridge, making statement 3 correct. It can also be used to determine mutual inductance, making statement 4 correct. Therefore, the correct answer is 1, 2, and 4.

The pole-zero patterns shown in the given figure indicate that all the poles and zeros are located on the unit circle in the complex plane. This characteristic is specific to an all-pass filter, which is a type of filter that allows all frequencies to pass through with equal gain, but introduces a phase shift. Therefore, the correct answer is an all-pass filter.

The maximum power handling capacity of a resistor depends on its thermal capacity. This is because when a resistor is subjected to high power, it generates heat. The thermal capacity of the resistor determines its ability to dissipate this heat and prevent overheating. If a resistor has a low thermal capacity, it may not be able to handle high power levels and could potentially fail or get damaged. Therefore, the thermal capacity of the resistor plays a crucial role in determining its maximum power handling capacity.

The piezoelectric crystal voltage sensitivity is defined as the field developed per unit stress. This means that the voltage developed in the crystal is directly proportional to the field that is generated when stress is applied to the crystal. The higher the stress applied, the stronger the field and therefore the higher the voltage developed. This sensitivity allows piezoelectric crystals to convert mechanical stress into electrical signals.

Strain gauges are used in load cells to measure the strain or deformation in an object. When a force is applied to the load cell, the strain gauges change their resistance due to the deformation of the object. This change in resistance is then converted into an electrical signal which can be measured and used to determine the force applied. Strain gauges are commonly used in various industries for applications such as weighing scales, force sensors, and structural health monitoring.

The loading effect refers to the change in the measurement caused by the instrument itself when connected to the circuit being measured. Instruments with low sensitivity are less likely to cause significant changes in the circuit because they require a larger input signal to produce a noticeable output. Therefore, instruments with low sensitivity are less likely to introduce errors or distortions in the circuit being measured, making them less prone to causing the loading effect.

The given equation y(n + 1) + 0.5n y(n) = 0.5x (n + 1) contains a term involving y(n), which indicates that the output at time n + 1 is dependent on the input and the output at time n. This implies that the system has memory, as it considers past inputs and outputs to determine the current output. Therefore, the equation is not attributable to a memoryless system.

The FM telemetry requires a channel that is 10 times of that required for AM telemetry because FM telemetry uses frequency modulation, which requires a wider bandwidth to transmit the signal compared to AM telemetry. FM telemetry uses a larger range of frequencies to encode the information, resulting in a higher data rate and a need for a larger channel to accommodate the wider bandwidth.

If statement 4 alone is correct, it means that BC-AD = -1. This condition is known as the determinant condition for reciprocity in a 2-port network. If this condition is satisfied, then the network is reciprocal. Therefore, the correct answer is 4 alone is correct.

The correct answer is "no cut-off input voltage". This means that there is no specific input voltage at which the current flow through the n-channel JFET is completely cut off. In other words, the JFET allows current to flow even at very low input voltages, unlike other devices where there is a specific voltage threshold below which no current flows.