AFCAT EKT Electrical Mock Test - 2 - AFCAT MCQ

If gain is high, damping ratio is small hence overshoot is more.

The mobility of electrons is more than that of holes because the probability of an electron having the energy required to move to an empty state in the conduction band is much greater than the probability of an electron having the energy required to move to the empty state in valance band. The mobility of hole is about half that of electrons.

Capacitive level transducer is an example of indirect measurement of level
The technique is frequently referred as RF as radio frequency signals applied to the capacitance circuit. The sensors can be designed to sense metrical with dielectric constants as low as 1.1 (coke and fly ash) and as high as 88 (water) or more.

Pre - emphasis is process of amplifying high frequency signals in spectrum before transmission of signal. It provides extra noise immunity because noise levels are higher at high frequencies there by pre-emphasis improves SNR at frequencies.
It is done before modulation of audio signal

Resonant frequency f₀ = Quality factor × Bandwidth
f₀ = 4000 × 2.4 × 10⁶ = 9.6 GHz

The Frequency Response of an amplifier is presented in a form of a graph that shows output amplitude (or, more often, voltage gain) plotted versus frequency. Typical plot of the voltage gain of an amplifier versus frequency. The gain is null at zero frequency, then rises as frequency increases, level off for further increases in frequency, and then begins to drop again at high frequencies. The frequency response of an amplifier can be divided into three frequency regions.
The frequency response begins with the lower frequency region designated between 0 Hz and lower cutoff frequency. At lower cutoff frequency f_L, the gain is equal to 0.707 A_mid. Amid is a constant midband gain obtained from the midband frequency region. The third, the upper frequency region covers frequency between upper cutoff frequency and above. Similarly, at upper cutoff frequency, f_H, the gain is equal to 0.707 A_mid. After the upper cutoff frequency, the gain decreases with frequency increases and dies off eventually.

Forbidden energy gap between valence band and conduction band is least in the case of impure silicon.

For x = 3, (x² – 8) > 0 so |x² - 8| = x² – 8

f(x) = x + (x² – 8)

f’(x) = 1 + 2x

f’(3) = 1 + 2(3) = 7

A dipole antenna is a linear antenna, usually fed in the center and producing maximum of radiation in the plane normal to the axis. It is said to be short dipole when length is less than λ / 4 and current distribution is sinusoidal. Radiation intensity is maximum along the normal to the dipole axis.

If G₀G₁G₂G₃ is a gray code number then the BCD equivalent number B0B1B2B3 can be estimated using:

B₃ = G₃

B₂ = B₃ ⊕ G₂

B₁ = B₂ ⊕ G₁

B₀ = B₁ ⊕ G₀

So, using the above rules, the BCD equivalent of gray code number 1001 is 1110

A working diode means the diode is biased or connected with the DC source. When a diode is forward biased (+ve terminal to anode and -ve terminal to cathode), it provides a low resistance path because it helps the majority carrier to crossover the barrier potential and conduct the flow of current. When a diode is reversed biased (-ve terminal to anode and +ve terminal to cathode) it provide a high resistance path because the majority carriers are flows away from the junction and no current conduction takes place.

Self-bias are emitter biased circuit. Generates it's own DC bias voltage .For the emitter which has a considerable effect, on the base current .Any circuit which does generate such bias voltage without actually directly depending on an explicit power supply is a self-bias.

The waves that travel close to the surface of the earth are known as surface waves.

Transformer oil is a highly refined mineral oil that is stable at high temperatures and has excellent electrical insulating properties. It is used in oil-filled transformers. Its function is to provide insulation and cooling.

Kinetic energy (KE = 1/2 mv²) represents energy the mass possesses by virtue of its motion. Likewise, potential energy (PE = mgh) represents energy the mass possesses by virtue of its position.
E = KE + PE
E is the total energy of the mass: i.e., the sum of its kinetic and potential energies. It is clear that E is a conserved quantity: i.e., although the kinetic and potential energies of the mass vary as it falls, its total energy remains the same and one form of energy is being converted into other form of energy.

Communication receiver is used for signal strength measurement as it is as the receiver end and due to which if the signal is not received properly from the sender we can easily determine the strength of the signal.
It is also used for detection and display of individual components of high-frequency wave as it enables us to display the components which comes at higher frequency and which comes at lower frequency

In case of DC series motor, field generated depends on armature current. At no load, current drawn is very less hence the field generated is less. Since the back emf remains constant hence speed is inversely proportional to the flux. Thus the initial speed will get very high and the motor may get damaged at no load.

Varactor diodes produces considerably less noise compared to other conventional diodes.

• These diodes are available at low costs.
• Varactor diodes are more reliable.
• The varactor diodes are small in size and hence, they are very light weight.
• The diode is operated in reverse bias.
• Increase in reverse bias of varactor diode increases the capacitance.
• Varactor diodes can be used as frequency modulators.
• In microwave receiver LO, varactor diodes can be used as frequency multipliers.
• Varactor diodes can be used as RF phase shifters.

IMPATT diode does both Microwave oscillations and amplification action due to its operation is based on supplying RF signal superimposed on the bias so as to amplify it by avalanche breakdown

1 farad = 1 coulomb/volt
One farad is defined as the capacitance of a capacitor which requires a charge of one coulomb to establish a potential difference of one volt between its plates.

Ethernet--→data link layer

Internet Protocol--→ network layer

Hyper text protocol--→application layer

Lorentz force is the combination of electric force  and magnetic force . Thus the Lorentz force is given by .

In an optical fiber with core and cladding refractive indices n₁ and n₂, the time dispersion Δt is given by:

Δt = (L n₁) / (c n₂ (n₁ - n₂))

L = length of the optic fiber, hence multipath time dispersion per unit length of fiber is:

Δt / L = (1.5) / (1 × 3 × 10⁸ (1.5 - 1)) = 2.5 ns/m

Equalizer rings are used in lap wounded armatures only to remove any circulating currents in parallel paths.

Conditional probability P(A|B):

P(A|B) = P(A ∩ B) / P(B) = [P(A) + P(B) – P(A ∩ B)] / P(B) = [1/4 + 1/3 – 1/2] / (1/3) = 1/4

Given,
Z₀ = 50 Ω and ZL = 40 + j30

Reflection co-efficient:
P = (Z_L - Z_₀) / (Z_L + Z_₀)
= (40 + j30 - 50) / (40 + j30 + 50)
= (-10 + j30) / (90 + j30)

|P| = √[(10)² + (30)²] / √[(90)² + (30)²]
= √(10) / 90

V.W.W.R = (1 + 1/3) / (1 - 1/3)
= 2

In positive feedback op-Amp acts in its saturation region

⇒ V_o = ±V_sat
V_o = 12 V

Angle between two vectors:

cos θ =  = 1/2

It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam.The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

Order of a differential equation is defined as the order of the highest order derivative and the degree of a differential equation, when it is a polynomial equation in derivatives, is defined as the highest power (positive integral index) of the highest order derivative.
The highest order derivative present in the given differential equation is d²y/dx², so it’s order is two. It is a polynomial equation in d²y/dx² and dy/dx and the highest power raised to d²y/dx² is one, so its degree is one.