Ongc Graduate Trainee Exam 2012 Free Online Practice Test
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FOR ELECTRONICS/ELECTRONICS & TELECOMMUNICATION BRANCH
EXAM TIME:3 HRS
EXAM QUESTIONS: 150
BREAKUP OF QUESTIONS:
TECHNICAL:80 QUESTIONS
GENERAL AWARENESS:40 QUESTIONS
APTITUDE:30 QUESTIONS
THERE IS NO NEGATIVE MARKING
- 1.
If the energy gap of semiconductor is 1.1 eV, then it would be
- A.
Opaque to the visible light
- B.
Transparent to the visible light
- C.
Transparent to the ultraviolet radiation
- D.
Opaque to the infrared radiation
Correct Answer
A. Opaque to the visible lightExplanation
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.Rate this question:
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- 2.
With increasing temperature, the electrical conductivity would
- A.
Increase in metals as well as in intrinsic semiconductors
- B.
Increase in metals but decrease in intrinsic semiconductors
- C.
Decrease in metals but increase in intrinsic semiconductors
- D.
Decrease in metals as well as in intrinsic semiconductors
Correct Answer
C. Decrease in metals but increase in intrinsic semiconductorsExplanation
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.Rate this question:
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- 3.
Energy Gap in Semi conductor's is
- A.
Transparent to shorter Wavelengths and Opaque to Larger wavelengths
- B.
Transparent to Longer Wavelengths and Opaque to Shorter Wavelengths
- C.
Transparent to both Longer wave and Shorter wave lengths
- D.
Opaque to both Longer wave and Shorter wave lengths
Correct Answer
B. Transparent to Longer Wavelengths and Opaque to Shorter WavelengthsExplanation
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.Rate this question:
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- 4.
Conductivity Of Intrinsic semi conductors depend up on
- A.
Temperature
- B.
Band Gap
- C.
Both a and b
- D.
None of these
Correct Answer
C. Both a and bExplanation
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.Rate this question:
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- 5.
Loading effect is primarily caused by instruments having
- A.
High resistance
- B.
High sensitivity
- C.
Low sensitivity
- D.
High range
Correct Answer
C. Low sensitivityExplanation
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.Rate this question:
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- 6.
A 3½ digit voltmeter having a resolution of 100 mV can be used to measure maximum voltage of
- A.
100V
- B.
200V
- C.
1000V
- D.
5000V
Correct Answer
A. 100VExplanation
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.Rate this question:
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- 7.
Match List I (Bridges) with List II (Parameters) and select the correct answer: List I A. Anderson bridge B. Kelvin Bridge C. Schering Bridge D. Wheal stone Bridge List II 1. Low Resistance 2. Medium Resistance 3. Inductance 4. Capacitance A B C D
- A.
4 2 3 1
- B.
3 2 4 1
- C.
3 1 4 2
- D.
4 1 3 2
Correct Answer
C. 3 1 4 2Explanation
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)Rate this question:
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- 8.
Load cell employ
- A.
Piezoelectric crystal
- B.
Capacitor
- C.
Mutual inductance
- D.
Strain gauges
Correct Answer
D. Strain gaugesExplanation
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.Rate this question:
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- 9.
Match List I (Devices) with list II (Characteristics) and select the correct answer: List I A. BJT B. MOSFET C. Tunnel diode D. Zener diode List II 1. Voltage controlled negative resistance 2. High current gain 3. Voltage regulation 4. High input impedance A B C D
- A.
1 4 2 3
- B.
2 4 1 3
- C.
2 3 1 4
- D.
1 3 2 4
Correct Answer
B. 2 4 1 3Explanation
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.Rate this question:
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- 10.
To avoid thermal runway in the design of an analog circuit, the operating point of the BJT should be such that it satisfies the condition
- A.
I V VCE = 1/2 VCC
- B.
VCE
- C.
VCE > 1/2VCC
- D.
VCE
Correct Answer
B. VCEExplanation
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.Rate this question:
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- 11.
Consider the following devices: 1. BJT in CB mode 2. BJT in CE mode 3. JFET 4. MOSFET The correct sequence of these devices in increasing order of their input impedance is
- A.
1,2,3,4
- B.
2,1,3,4
- C.
2,1,4,3
- D.
1,3,2,4
Correct Answer
A. 1,2,3,4Explanation
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.Rate this question:
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- 12.
Consider the following statements for a 2- port network: 1. Z11 = Z22 2. h 12 = h 21 3. Y12= - Y21 4. BC-AD = - 1 The network is reciprocal if and only if
- A.
1 and 2 are correct
- B.
2 and 3 are correct
- C.
3 and 4 are correct
- D.
4 alone is correct
Correct Answer
D. 4 alone is correctExplanation
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.Rate this question:
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- 13.
On closing switch ‘S’ the circuit in the given figure is in steady-state. The current in the inductor after opening the switch ‘S’ will
- A.
Decay exponentially with a time constant of 2 s constant of 2s
- B.
Decay exponentially with a time constant of 0.5s
- C.
Consist of two decaying exponential each with a time constant of O.5s
- D.
Be oscillatory
Correct Answer
B. Decay exponentially with a time constant of 0.5sExplanation
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.Rate this question:
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- 14.
Match List I with list II for the driving point impedance synthesis and select the correct answer: List (form) A. Cauer I B. Cauer II C. Foster I D. Foster II List II (Networks) 1. L in series aims and C in shunt arms of a ladder 2. C in series arms and L in shunt arms of a ladder 3. Series combination of L and C in parallel 4. Parallel combination of L and C in series A B C D
- A.
1 2 3 4
- B.
1 2 4 3
- C.
2 1 4 3
- D.
2 1 3 4
Correct Answer
A. 1 2 3 4Explanation
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.Rate this question:
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- 15.
Poles and zeros of a driving-point function of a network are simple and interlace on the jw axis. The network consists of elements
- A.
R and C
- B.
L and C
- C.
R and L
- D.
R, L and C
Correct Answer
A. R and CExplanation
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.Rate this question:
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- 16.
The discrete-time equation y(n + 1) + 0.5n y(n) = 0.5x (n + 1) is NOT attributable to a
- A.
Memoryless system
- B.
Time-varying system
- C.
Linear system
- D.
Causal system
Correct Answer
A. Memoryless systemExplanation
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.Rate this question:
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- 17.
The maximum power handling capacity of a resistor depends on
- A.
Total surface area
- B.
Resistance value
- C.
Thermal capacity of the resistor
- D.
Resistivity of the material used in the resistor
Correct Answer
C. Thermal capacity of the resistorExplanation
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.Rate this question:
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- 18.
Match List I (Bridges) with List II (Quantities) and select the correct answer List I A. Maxwell’s bridge B. Wien bridge C. Hay’s bridge D. Schering bridge List II 1. Frequency 2. Inductance with value of Q < 10 3. Capacitance 4. Inductance with value of Q > 10 A B C D
- A.
2 1 4 3
- B.
4 3 2 1
- C.
4 1 2 3
- D.
2 3 4 1
Correct Answer
A. 2 1 4 3 -
- 19.
Gauge factor of a strain gauge is defined as the ratio of a per unit change in the
- A.
Conductivity to the per unit change in applied force acting on the element
- B.
Resistance to the per unit change in the length of the element
- C.
Stress to the per unit change in strain of the element
- D.
Current to the per unit change in the length of the element
Correct Answer
B. Resistance to the per unit change in the length of the elementExplanation
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.Rate this question:
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- 20.
For an AM wave, the maximum voltage was found to be 10 V and the minimum voltage was found to be 5 V. The modulation index of the wave would be
- A.
Conductivity to the per unit change in applied force acting on the element 0.33
- B.
Resistance to the per unit change in the length of the element 0.52
- C.
0.40
- D.
0.1
Correct Answer
A. Conductivity to the per unit change in applied force acting on the element 0.33 -
- 21.
Hot wire anemometer is a device used to measure the
- A.
Pressure in gases
- B.
Liquid discharge
- C.
Gas velocities
- D.
Temperature
Correct Answer
C. Gas velocitiesExplanation
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.Rate this question:
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- 22.
The FM telemetry as compared with AM telemetry requires a channel that is
- A.
Equal to that of AM telemetry
- B.
Smaller than what is required for AM telemetry
- C.
100 times of that required for AM telemetry
- D.
10 times of that required for AM telemetry
Correct Answer
D. 10 times of that required for AM telemetryExplanation
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.Rate this question:
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- 23.
Digital measuring instruments use the following three types of A to D converters 1. Dual Slope Type 2. Counter Type 3. Flash Type The correct sequence for these converters in decreasing order of their speed is
- A.
3, 1, 2
- B.
1, 2, 3
- C.
2, 3, 1
- D.
3, 2, 1
Correct Answer
D. 3, 2, 1Explanation
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.Rate this question:
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- 24.
Consider the following statements regarding the advantages of Anderson bridge: 1. It is the modification of the Maxwell’s inductance-capacitance bridge. 2. For measuring the low Q of coils, it is superior to the Maxwell’s bridge. 3. It is simple compared to Maxwell’s bridge. 4. It can be used to determine mutual inductance also
- A.
1, 2 and 3
- B.
1, 2 and 4
- C.
2 and 4
- D.
1, 3 and 4
Correct Answer
B. 1, 2 and 4Explanation
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.Rate this question:
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- 25.
The output current versus input voltage transfer characteristic of an n-channel JFET is such that there is
- A.
Zero current flow at zero input voltage bias
- B.
Current flow only when a positive input threshold voltage is crossed
- C.
Current flow only when a negative input cut-off voltage bias is crossed
- D.
No cut-off input voltage
Correct Answer
D. No cut-off input voltageExplanation
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.Rate this question:
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- 26.
Assertion (A): A circuit containing reactances is said to be in resonance if the voltage across the circuit is in phase with the current through it. Reason (R): At resonance, the power factor of the circuit is zero.
- A.
Both A and R are true and R is the correct explanation of A
- B.
Both A and R are true but R is NOT the correct explanation of A
- C.
A is true but R is false
- D.
A is false but R is true
Correct Answer
C. A is true but R is falseExplanation
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.Rate this question:
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- 27.
The pole-zero patterns shown in the given figure is for
- A.
A low - pass filter
- B.
A high-pass filter
- C.
An all - pass filter
- D.
A band - pass filter
Correct Answer
C. An all - pass filterExplanation
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.Rate this question:
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- 28.
An op-amp has open-loop gain 100000 and the open- loop upper cut-off frequency is 20 Hz. The unity-gain frequency of the op-amp is
- A.
2 MHz
- B.
1 MHz
- C.
3 kHz
- D.
2 kHz
Correct Answer
A. 2 MHzExplanation
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.Rate this question:
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- 29.
(Measured Quantities) and select the correct answer List I A. Capacitive transducer B. Thermocouple C. Load cell D. Diaphragm List II 1. Pressure 2. Torque 3. Displacement 4. Temperature A B C D
- A.
2 4 3 1
- B.
3 1 2 4
- C.
2 1 3 4
- D.
3 4 2 1
Correct Answer
D. 3 4 2 1 -
- 30.
The piezoelectric crystal voltage sensitivity is defined as a
- A.
Voltage developed per unit stress
- B.
Field developed per unit stress
- C.
Voltage developed per unit force
- D.
Field developed per unit force
Correct Answer
B. Field developed per unit stressExplanation
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.Rate this question:
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- 31.
- A.
Causal, linear and time-varying
- B.
Causal, non-linear and time-varying
- C.
Non-causal, linear and time-varying
- D.
Non-causal, non-linear and time-variant
Correct Answer
C. Non-causal, linear and time-varying -
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Dec 14, 2023Quiz Edited by
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