Full Test 5 - EKT EEE - AFCAT MCQ

Total balls in the bag are = 15
Sample space =15_c3
The probability that all the balls are red is = 

Let the side of the square is x

Now, the area of square is, A = x²

Given that area of the square increased by 69%, the area will be 1.69 A

Let the increased side of the square is nx 

⇒ (nx)² = 1.69x²
⇒ n = 1.3
Hence the side of the square increases by 30%

The inverse Laplace transform, 

Multiplying matrix A by itself, we get A²= 

Similarly, 

In an AC circuit, resonance occurs when capacitive reactance equals reactive reactance.

At resonance, X_L=X, Z=R

The current at a point in the circuit is the amount of charge that passes that point in one second. A current of 1 A is flowing in a circuit if a charge of 1 coulomb passes any point in the circuit every second.

Tesla (T) is a measure of magnetic flux density.

Electrical potential measures in volts (V).

Magnetic potential measures in Amperes (A).

By conservation of angular momentum

I’ω’ = Iω

(M + 2m) r²ω’ = Mr²ω

Reverberation is the time taken for the sound to fall below the minimum audibility measured from the instant when the source stopped sounding. Therefore if the reverberation time becomes too large it produces an echo.

Optical fibre works on the principle of total internal reflection. Here light is used to transmit information from one place to another.

In circuit switching entire channel capacity is used for single communication.
Two types of switched services are used in Wide Area Network:
(1). Circuit Switching: In circuit switching, a dedicated channel, called circuit, is set up between two stations for the duration of the transmission.The circuit must be established to make a complete end-to-end  connection before any data transmission.The whole bandwidth is dedicated to to this connection even if no data is being transferred.
(2). Packet Switching: In packet switching there is no dedicated circuit between any two end nodes, links can be dynamically shared among several communications over time. To provide the link sharing, user data must be segmented into discrete, variable length units called packets.

The Schottky diode is a semiconductor formed by the junction of a semiconductor with metal. It has a low forward voltage drop and near zero reverse recovery time hence used in very fast switching circuits.

The charge carriers in an n-channel FET are electrons alone

Tunnel diode owing to heaving doping(typically 100 to several thousand times normal doping semiconductor diode) resulting in extremely small depletion layer width. Due to this extremely thin depletion region width the charge carriers can "tunnel" through depletion region

In an unbiased pn junction when the Total current crossing the junction from p - side to n - side equals the total current crossing the junction from n - side to p - side then the current is said to be zero current. 

The Zener Diode because of its stable output characteristic, is used as a constant voltage source, gate electrode on the FET corresponds to the base in bipolar transistor and the SCR is a silicon rectifier with a gate electrode to control when current flows from anode to cathode.

The oscillation frequency of an RC phase shift oscillator using three identical RC sections is 

If both inputs of JK flip flop are same, then it acts as T flip flop. If both the inputs are low, then the output will be same as the previous output. If both the inputs are high, then the output will be complement of the previous output.

The below truth table is for OR gate.

 

From the above truth table we can say that if one of the input is high, the output will be high.

The below truth table is for AND gate.

From the above truth table we can say that if one of the input is low, the output will be high.

Converting in decimal we have

A full adder can be realized by using two half adders and one OR gate.

A multiplexer has many inputs and one output and selection lines.

• D.C. motor is preferred over an A.C. motor when we need variable speed operation because As in DC series motor field winding and armature winding is in series. So whenever armature current changes field current also changes as they are same due to which its torque changes rapidly and we get a variable speed.
• While in AC motor for same purpose we require frequency change which requires another complex circuitry

Advantages of DC motors:

• The attractive feature of the dc motor is that it offers the wide range of speed control both above and below the rated speeds.
• Dc series motors are termed as best suited drives for electrical traction applications used for driving heavy loads in starting conditions.

• Quick starting, stopping, reversing and acceleration

• Free from harmonics, reactive power consumption and many factors which makes dc motors more advantageous compared to A.C induction motors.

The efficiency of the transformer is maximum at when copper loss is equal to iron loss.

A dc series motor should always be started on load. When the motor is connected across the supply mains without load, it draws small current from the supply mains flowing through the series field and armature, the speed tends to increase so that back emf may approach the applied voltage in magnitude. The increase in back emf weakens the armature current and hence the field current. This cause again increase in speed so in back emf. Thus the field continues to weaken and speed continues increase until the armature produced such centrifugal force that it is coming out from its shaft and gets damaged.

The stator frame consists of laminations of silicon steel, usually with a thickness of about 0.5 millimetre. Lamination is necessary since a voltage is induced along the axial length of the steel as well as in the stator conductors. The laminations are insulated from each other usually by a varnish layer. This breaks up the conducting path in the steel and limits the losses (known as eddy current losses) in the steel.

All the flux in the transformer will not be able to link with both the primary and secondary windings. A small portion of flux will link either winding but not both. This portion of flux is called leakage flux. Due to this leakage flux in transformer, there will be a self-reactance in the transformer windings.

Diffusion is a physical process where molecules of a material move from an area of high concentration (where there are many molecules) to an area of low concentration (where there are fewer molecules).