# Why the cutoff frequency is taken for 3db?

Why the cutoff frequency is taken for 3db?

## Related questions

Description : What is meant by 3db frequency?

Answer : When Q-point is at cut off region means it is just above the horizontal axis VCE

Description : What do you mean by frequency response of an amplifier?

Description : What is the best frequency response?

Description : What is the frequency response of a circuit?

Answer : MOSFET provides better efficiency at high frequency and its high speed switching losses are less hence MOSFET is used for high frequency.

Description : Consider the sinusoidal voltage waveforms, v1(t) and v2(t), as shown  (i) State the frequency and amplitude for both the voltage waveforms. (ii) Calculate the rms value of v1(t) and v2(t), ... time domain. (vii) Calculate the instantaneous value of v2(t) at t = 38 ms.

Description : Which of the following thyristors can be used for high frequency of operation? A) TRIAC B) DIAC C) SCR D) GTO

Answer : Which of the following thyristors can be used for high frequency of operation? A) TRIAC B) DIAC C) SCR D) GTO

Description : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage:  (A) Eddy Current and Hysteresis losses will be ... Current will be too much high  (C) Transformer may start to smoke and burn  (D) No effect

Answer : What would happen if a power transformer designed for operation on 50 Hz (frequency) were connected to a 500 Hz (frequency) source of the same voltage:  (A) Eddy Current and Hysteresis losses will be ... will be too much high  (C) Transformer may start to smoke and burn  (D) No effect

Description : For measurement of radio frequency ac signals __________ type meter is used

Answer : For measurement of radio frequency ac signals thermo-couple type meter is used

Description : For a 500 Hz frequency excitation, a 50 km long power line will be modeled as

Answer : For a 500 Hz frequency excitation, a 50 km long power line will be modeled as long line

Description : For a frequency of 200 Hz, the time period will be?

Answer : For a frequency of 200 Hz, the time period will be 0.005 s.

Answer : For measuring current at high frequency we should use thermocouple instrument.

Description : For given applied voltage, with the increase in frequency of the applied voltage?

Answer : For given applied voltage, with the increase in frequency of the applied voltage eddy current loss will remain unchanged.

Description : Which capacitor is used for high frequency?

Description : Sinusoids find amplitude, period, frequency, voltage (Problem 1)

Answer : Sinusoids find amplitude, period, frequency, voltage (Problem 1)

Description : Principal of digital frequency meter.

Answer : The basic block diagram of basic digital frequency meter (DFM) is shown in above figure. The signal whose frequency we have to be measured is first to be amplified through amplifier. The output of amplifier ... = Number of counts. t = Time interval between start and stop condition of the gate.

Description : Define the following terms: 1) Virtual height 2) Actual height 3) Critical frequency. 4) Maximum usable frequency.

Answer : 1) Virtual height:- The incident and refracted rays follow paths that are exactly the same as they have been if reflection had taken place from a surface located at a greater height, called ... angle of incidence is other than the normal is known as maximum unstable frequency. MUF= fc secθ

Description : Draw the diagram and explain the working of ferrodynamic type frequency meter.

Answer : Ferrodynamic type frequency meter: (Electrical resonance type frequency meter): It consists of a fixed coil. The supply whose frequency is to be measured is connected across it. This coil ... so selected that the moving coil takes up a convenient position when frequency is of normal value.

Description : List the different types of frequency meters.

Answer : Different types of frequency meters  1. Reed type [Mechanical type] 2. Ferro-dynamic type [Resonances type] 3. Weston type 4. Ratio-meter type 5. Saturable core type 6. Digital type

Description : Explain working of Weston type frequency meter.

Answer : Weston Type Frequency Meter: There are two fixed coils marked as A and B. Each coil divided into two equal parts and are fixed such that their magnetic axis are perpendicular to each ... leading to deflections in either direction depending on the currents there in, due to changed impedances.

Description : State the application of phase sequence indicator; clip on ammeter, frequency meter & P.F. meter.

Answer : Phase Sequence Indicator:  1. For finding correct phase sequence of supply  2. For obtaining exact instant of parallel operation of alternators.  3. For obtaining reversal of rotation ...  4. In electroplating industries   5. In various processes industries for measuring power factor

Description : List two types of oscillator, which generates frequency in RF range.

Answer : Types of Oscillators generating frequencies in RF range: i) Hartley Oscillator ii) Colpitt’s Oscillator iii) Clapp Oscillator

Description : State the need of multistage amplifier. Draw frequency response of R-C coupled amplifier.

Answer : The need of multistage amplifier The voltage (or power) gain, obtained from a single stage small signal amplifier, is limited. Therefore, it is not sufficient for all practical applications. Therefore, in ... to use a MULTISTAGE AMPLIFIER .  Frequency response of R-C coupled amplifier.

Description : Classify the transformers based on the construction, frequency and power.

Answer : Classification of Transformer Based On: i) Construction: Shell type, Core type, Berry type ii) Change in voltage level: Step-Up, Step-Down, iii) Number of phases: Single phase, Three phase iv) ... Control vi) Cooling: Self-cooled, Air-cooled, Forced-air cooled, Oil-cooled, Forced-oil cooled.

Description : Define: 1) frequency, 2) cycle, 3) time period, 4) amplitude

Answer : 1) frequency: The total number of cycles completed in one second is called frequency. Its unit is cycles per second or Hertz (Hz). Its formula is f = 1/ T, where T is time period. ... is second per cycle. 4) amplitude: the maximum instantaneous value of sine wave is called as amplitude.

Description :  A pulse radar has a pulse repetition frequency (PRF) of 3 KHz. If the radar is emitting at 10 GHz, what is the maximum unambiguous range for this radar? A) 5 Km B) 5 m C) 50 Km D) 15 m

Answer :  A pulse radar has a pulse repetition frequency (PRF) of 3 KHz. If the radar is emitting at 10 GHz, what is the maximum unambiguous range for this radar? A) 5 Km B) 5 m C) 50 Km D) 15 m

Description : A pulse compression radar transmits an encoded pulse having a frequency chirp from 990 MHz to 1010 MHz centred around 1 GHz. The range resolution capability of this radar is A) 7.5 m B) 7.5 Km C) 75 m D) 750 m

Answer : A pulse compression radar transmits an encoded pulse having a frequency chirp from 990 MHz to 1010 MHz centred around 1 GHz. The range resolution capability of this radar is 7.5 m

Description : The clock frequency of an 8085 microprocessor based system is 3 MHz. What should be the minimum pulse width of the INTR signal so that it is recognized successfully? A) 5.6 µs B) 5.7 µs C) 5.8 µs D) 5.9 µs

Answer : The clock frequency of an 8085 microprocessor based system is 3 MHz. What should be the minimum pulse width of the INTR signal so that it is recognized successfully? A) 5.6 µs B) 5.7 µs C) 5.8 µs D) 5.9 µs

Description : What is the frequency range of VHF electromagnetic waves? A) 30-300 kHz B) 30-3000 kHz C) 30-300 MHz D) 30-3000 MHz

Answer : What is the frequency range of VHF electromagnetic waves? A) 30-300 kHz B) 30-3000 kHz C) 30-300 MHz D) 30-3000 MHz

Description : The SCR would be turned OFF by voltage reversal of applied anode-cathode ac supply frequency of A) 10 kHz B) 10 Hz C) 5 kHz D) 5 Hz

Description : In a series R-C circuit, with the increase in frequency, current (A) Reduces (B) Increases (C) Does not change (D) Becomes zero

Answer : In a series R-C circuit, with the increase in frequency, current Increases

Description : A series R-L-C Circuit has a resonant frequency of 1000 Hz. If the values of R, L and C are doubled, the new resonant frequency is

Answer : A series R-L-C Circuit has a resonant frequency of 1000 Hz. If the values of R, L and C are doubled, the new resonant frequency is 500 Hz

Description : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque  (1) Decreases (2) Increases (3) Remains constant (4) None of the above

Answer : The speed of a three-phase induction motor is controlled by variable voltage variable frequency control (i.e. keeping V/f constant). As the frequency is reduced, the slip at maximum torque Increases

Description : In a series RLC high Q circuit, the current peaks at a frequency  (1) equal to the resonant frequency (2) greater than the resonant frequency (3) less than the resonant frequency (4) equal to half the resonant frequency

Answer : In a series RLC high Q circuit, the current peaks at a frequency equal to the resonant frequency

Description : In a self-controlled synchronous motor fed from a variable frequency inverter  (1) the rotor poles invariably have damper windings  (2) there are stability problems  (3) the speed of the rotor decides stator frequency  (4) the frequency of the stator decides the rotor speed

Answer : In a self-controlled synchronous motor fed from a variable frequency inverter the frequency of the stator decides the rotor speed

Description : What is the frequency of an alternator which has 2 poles and makes 3600 revolutions per minute? A) 3600 HZ B) 60 Hz C) 120 Hz D) None of these

Answer : What is the frequency of an alternator which has 2 poles and makes 3600 revolutions per minute? A) 3600 HZ B) 60 Hz C) 120 Hz D) None of these

Description : What happens to the voltage in the secondary when the frequency of the supply in the primary is decreased? A) It increases B) It decreases C) It remains the same D) Cannot say unless the actual percentage increase in the frequency is known

Answer : What happens to the voltage in the secondary when the frequency of the supply in the primary is decreased? A) It increases B) It decreases C) It remains the same D) Cannot say unless the actual percentage increase in the frequency is known

Description : The device which allows reverse power flow and withstands highest switch frequency is (A) GTO (B) MOSFET (C) IGBT (D) Inverter grade SCR

Answer : The device which allows reverse power flow and withstands highest switch frequency is MOSFET

Description : The time period of third harmonic of power supply frequency, in milliseconds, is (A) 20 (B) 3.33 (C) 6.66 (D) 60

Answer : The time period of third harmonic of power supply frequency, in milliseconds, is 6.66

Description : Two waves have frequency of 500 Hz. One is set at its maximum value whereas the other at zero. The phase angle between them will be

Answer : Two waves have frequency of 500 Hz. One is set at its maximum value whereas the other at zero. The phase angle between them will be 90o

Description : A 4 GHz carrier is amplitude modulated by a low-pass signal of maximum cut off frequency 1 MHz. lf this signal is to be ideally sampled, the minimum sampling frequency should be nearly

Answer : A 4 GHz carrier is amplitude modulated by a low-pass signal of maximum cut off frequency 1 MHz. lf this signal is to be ideally sampled, the minimum sampling frequency should be nearly 4 Ghz

Description : In a 741 Op-Amp, there is 20 dB/decade fall-off starting at a relatively low frequency. This is due to the (A) applied load (B) internal compensation (C) impedance of the source (D) power dissipation in the chip

Answer : In a 741 Op-Amp, there is 20 dB/decade fall-off starting at a relatively low frequency. This is due to the internal compensation

Description : An accelerometer has input range of 0 to 10g, natural frequency 30 Hz and mass 0.001 kg. The range of the secondary displacement transducer in mm required to cover the input range is (A) 0 to 2.76 (B) 0 to 9.81 (C) 0 to 11.20 (D) 0 to 52.10

Answer : An accelerometer has input range of 0 to 10g, natural frequency 30 Hz and mass 0.001 kg. The range of the secondary displacement transducer in mm required to cover the input range is 0 to 2.76

Description : The frequency of an alternating current is?

Answer : The frequency of an alternating current is the number of waves passing through a point in one second.

Description : The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of?

Answer : The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of iron loss in core.

Description : In a series L-C circuit at the resonant frequency the?

Answer : In a series L-C circuit at the resonant frequency the current is maximum.

Description : In R-L-C series resonant circuit magnitude of resonance frequency can be changed by changing the value of?

Answer : In R-L-C series resonant circuit magnitude of resonance frequency can be changed by changing the value of L or C.

Description : Two waves of the same frequency have opposite phase when the phase angle between them is?

Answer : Two waves of the same frequency have opposite phase when the phase angle between them is 180°.

Answer :  A sine wave has a frequency of 50 Hz. Its angular frequency is 100 n radian/second.

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