The Indian Air forces actual paper based on electronics and communications questions and science related questions.Indian Air forces paper consists of multiple choice questions.
Questions based on electronics and communications:
1. In a communication system, noise is most likely to get into the system
(A) At the transmitter
(B) In the channel
(C) In the information source
(D) At the destination
2. When modulation frequency is doubled, the modulation index is halved, and the modulating voltage remains constant, the modulation system is
(A) Amplitude modulation
(B) Phase modulation
(C) Frequency modulation
(D) Angle modulation
3. Impedance inversion may be obtained with
(A) A short – circuited stub
(B) An open – circuited stub
(C) A quarter – wave line
(D) A half – wave line
4. HIGH frequency waves are
(A) Observed by the F2 layer
(B) Reflected by D layer
(C) Capable of use for long-distance communication on the moon
(D) Affected by the solar cycle
5. Which one of the following terms does not apply to the Yagi-uda array?
(A) Good band width
(B) Parasitic elements
(C) Folded dipole
(D) High gain
6. A duplexer is used
(A) To couple two different antennae to a transmitter without mutual interference
(B) To allow one antenna to be used for reception or transmission without mutual interference
(C) To prevent interference between two antennae when they are connected to receiver
(D) To increase the speed of the pulses in the pulsed radar
7. Indicate which of the following system is digital
(A) Pulse – Position modulation
(B) Pulse – Code modulation
(C) Pulse – Width modulation
(D) Pulse – Frequency modulation
8. A forward error correcting code corrects errors only doubt
(A) Requiring partial retransmission of the signal
(B) Requiring retransmission of entire signal
(C) Using parity to correct to errors in all cases
(D) Requiring no part of the signal to be transmitted
9. A typical signal strength received from a geosynchronous communication satellite is of the order of doubt
(A) A few milli watts
(B) Kilo watts
(D) Few pico watts
10. Telephone traffic is measured doubt
(A) With echo cancellers
(B) By the relative congestion
(C) In terms of the grade of service
(D) In erlangs
11. Positive logic in a logic circuit is one in which doubt
(A) Logic 0 and 1 are represented by 0 and positive voltage respectively
(B) Logic 0 and 1 are represented by negative and positive voltages respectively
(C) Logic 0 voltage level in higher than logic 1 voltage level
(D) Logic 0 voltage level is lower than logic 1 voltage level
12. A half-adder can be made from
(A) Two NAND gates
(B) A NOT gate and an OR gate
(C) An AND gate and an OR gate
(D) An AND gate and an X-OR gate
13. Which of the following devices has its characteristics very close to that of an ideal current source?doubt
(A) Field effect transistor
(B) Transistor in common bas mode
(C) Zener diode
14. The main use of a common base transistor amplifier is
(A) As voltage amplifier-> CE
(B) Current amplifier (CB for HF applications)
(C) For matching a high source impedance to a low load impedance ->CC
(D) For rectification of a.c. signal -> any confi but generally CE
15. A class-B amplifier is biased
(A) Just at cut-off
(B) Nearly twice cut-off
(C) At mid point of load line
(D) so that IB equals jut IC
16. If the peak transmitted power in a radar system is increased by a factor of 16, the maximum range will be increased by a factor of
(A) 2 (B) 4 (C) 8 (D) 16
17. A high PRF will (indicate the false statement) doubt
(A) Make the returned echoes easier to distinguish from noise
(B) Make target tracking easier with conical scanning
(C) Increase the maximum range
(D) Have no effect of the range resolution
18. A solution to the “blind speed” problem in a radar system is to
(A) Change the Doppler frequency
(B) Vary the PRF
(C) Use mono pulse
(D) Use MTI
19. The number of active picture elements in a television image depends on
(A) Fly back time
(B) CRT screen size
(C) Received band width
(D) FB ratio of receiver antenna
20. In a color TV, the three primary colors are
(A) Red, orange and blue
(B) Red, blue and green
(C) Red, green and yellow
(D) Red, orange and green
Science based questions:
1.Capacitance of a cell measured in..? =Farad
2.To made House use electric heater which metal/element is better..?
3. Internal resistance of ideal current source..? = Infinite
4. Integral of (dx / (xlogx))…?
5. Earth &geostationary satellites have same /relative = angular velocity
a.accleraton b.velocity c.angular velocity
6. Sound waves are= .Longitudinal
A .Longitudinal B. Transverse C both D .neither.
7. Demultiplxer can called as ..? Ans. data distributor
8. Set of instructions meant for to do some task is called. Ans…Programme
9. Properties Alkali metals..
10. Break down occurs in diode because of.
11. If u wants to connect two systems through telephone line which of the following u will use..? Modem
A. Bus B.Modem C.Router
12. Inductor opposes sudden changes in… Ans…Current
13. Which is renewable energy..
a. petrol b.Coal c.Wind energy d.nuclear
14. Which material is widely used for making solar cell?
15. Cell converts.
A. Chemical energy into electric energy
B. electric energy into chemical energy
16. Steel pipes made from…
17. Human being is
A. open loop sys’m
B.closed loop sys’m with single feed back.
C. closed loop sys’m with multiple feed back.
18. If the gain of the open loop sys’m is doubled then gain margin will become.. = halved ie 2* 1/2 will give |G.H|= 1
19. Corrosion of aluminum is not formed because of..?
20. If the speed flow in pipe of diameter 6 mm is 5m/s.If this pipe is connected to another of diameter 3 mm, then speed will be..
21. They give change in force and change in diameter of a square plate. Ask us to find change in pressure…= Force* Area
22. They give three sets of measurements .Which are sets forms
23. Names, numbers and other information used to solve the problems of..
a.contrlo b.data c. instruction.
24. First aid of electrical shock victim..? Wood, switch off the mains
25. The performance (function) of fuse doesn’t depend on..
a. Type of material b .Length of the material..
26. Annealing makes the material… (Effect of annealing) = Cooling the metal slowly to make it
Electronics & Communication Paper
1. Sampling is helpful for..? A to D conversion
2. Sound waves are (It came in both papers)
a .Longitudinal b. Transverse c. Electro magnetic d.Gravitational
3. If two identical capacitors connected parallel then effective capacitance..? C1+C2
4. Wein bridge is used to measure.. Ans…Frequency
5. Which configuration has min distortion..?
a. CLASS A b. CLASS B c. CLASS C d. CLASS AB
6. Which of the following is not system software..?
a. Linker b. Loader. c. Compiler d. none
7. Min No, of NAND gates required to realize the function AB= 2 (ANDing oprn)
8. Flip Flops mainly used for..? Data storage
9. Which is noise free..
a. AM b. FM.. c. Both d .none
10. Terrestrial TV propagation System used in India
a. PAL b. NTSC c. DFS
11. Skin depth of an waveguide doesn’t depend on.. Doubt Skin Depth= 1/sqrt(pi*f*u*conductivity)
a. freq b. temp c .length of the conductor d.Type of material
12. Transformer rating expressed in = primary: secondary voltage
13. Electrical energy can be measured using.. Newtons
14. An ideal opamp has….Ans..Infinite B.W
15. Restivity range of semiconductor..?
16. They give modulation index, carrier power ask us to find total power.. Pt= Pc(1+(sqr of m)/2)
17. In JFET if Vds increased what happen to Ids.? Its typical chara says Ids will enter into: i) Linear region ii) sqr law region iii) constant current iv) const vtg
18. They give some freq and ask us to find Image Freq…? Fi= Fs+ 2*Fif
19. In an Unbiased semiconductor the current is zero because of.. =No current due to minority carrier(Ideal cond)
20. If BJT is in Cutoff region
A. Max voltage appears across load
B. a.Max voltage appears across Transistor.
21. Decibel used to measure doubt
a. power b. voltage c .current d .power level
22. In RC coupling the value of C should be high because.. T=RC, it will form good filter for rectifier
23. An ideal voltage source charges capacitor in = infinite time
24. They give Vmax and Vmin and ask us to find modulation index? m= (Vmax-Vmin)/ (Vmax+Vmin)
25. A voltage source of 5v with internal resistance 2 ohm can transfer max power to load when the value of load resistance is… Load R= 2 ohm, Pmax= sqr of Vs/ (4R)
26. One question electric motor. While switching on motor load should be present. If not what will happen. Some thing like this. I didn’t remember exactly..
27. Polarization in a dielectric is given by
A. P=xE B. P= (1-x) E C.P= xeE e=permivity…x=suspectance
I hope you can prepare Indian Air force exam to see this actual paper .