Attempt the ISRO Electronics & Communication (ECE) 2011 previous year paper in real CBT exam mode or practice mode with verified answers and explanations.
All ISRO Electronics & Communication (ECE) papers
80 questions.
Topic: Optoelectronics
_____ is used to describe the light gathering or light collecting ability of an optical fiber
Answer: C. Numerical aperture
Explanation: Detailed explanation not provided in the source.
Topic: Digital Circuits
_____ has the maximum fan out capacity
Answer: B. CMOS
Explanation: Detailed explanation not provided in the source.
Topic: Signals and Systems
If Z transform of $x(n)$ is $X(z)$ then the Z transform of $x(n-k)$ is
Answer: C. $z^{-k}X(z)$
Explanation: $x(n-k) \xrightarrow{z-transform} z^{-k}X(z)$
Topic: Digital Circuits
The following code will implement a
process (clk, d) begin
If $(clk='1')$ then
$q<=d$;
end if;
end process
Answer: C. A latch
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
In phase modulated signal, the frequency deviation is proportional to
Answer: C. Both (a) and (b)
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
For a fast communication which of the following requirements have to be met
Answer: C. High channel capacity
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
For an earth station transmitter input power of 40 dBW (10,000 W), with a back off loss of 3 dB, a total branching and feeder loss of 3 dB, and a transmit antenna gain of 40 dB, determine the EIRP.
Answer: B. 74 dBW
Explanation: $EIRP = P_{t} + G_{t} - L_{backoff} - L_{(branching+feeder)} = 40 + 40 - 3 - 3 = 80 - 6 = 74~dBW$.
Topic: Electronic Devices
The transconductance $g_{m}$ of an FET in the saturation region equals
Answer: A. $\frac{-2I_{DSS}}{V_{p}}[1-\frac{V_{GS}}{V_{p}}]$
Explanation: $I_{DS}=I_{DSS}(1-\frac{V_{GS}}{V_{P}})^{2}$. $g_{m}=\frac{\partial I_{D}}{\partial V_{GS}}=\frac{-2I_{DSS}}{V_{p}}(1-\frac{V_{GS}}{V_{p}})$.
Topic: Analog Circuits
The transistor amplifier with 85% of efficiency is likely to be
Answer: D. Class C
Explanation: Detailed explanation not provided in the source.
Topic: Computer Organization
A run-time stack cannot be used in a round-robin scheduling system because of the nature of scheduling
Answer: A. LIFO (Last in First out)
Explanation: Detailed explanation not provided in the source.
Topic: Mathematics
$(3+i)/(5+5i)$ is same as
Answer: A. $(2-i)/5$
Explanation: $\frac{3+i}{5+5i}=\frac{3+i}{5(1+i)}\times\frac{1-i}{1-i}=\frac{3-3i+i+1}{5(1+1)} = \frac{2(2-i)}{5\times2}=\frac{(2-i)}{5}$.
Topic: Digital Circuits
The greatest negative number which can be stored in a 8-bit register using 2's complement arithmetic is
Answer: D. -128
Explanation: Detailed explanation not provided in the source.
Topic: Network Theory
Two coupled coils have self inductances $L_{1}=10~mH$ and $L_{2}=20~mH$. The coefficient of coupling (K) being 0.75 in the air. Voltage in the second coil when the current in circuit is given by I = 2 sin(314 t) A is
Answer: C. 6.66 cos(314t) V
Explanation: $M=K\sqrt{L_{1}L_{2}} = 0.75\sqrt{10\times10^{-3}\times20\times10^{-3}}=0.0106$. $V_{2}=M\frac{di}{dt}=0.0106\times2\times314~cos(314~t) = 6.66~cos(314~t)V$.
Topic: Communication Systems
In a radar system, if the peak transmitted power is increased by a factor of 16 and the antenna diameter is increased by a factor of 2, then the maximum range will increase by a factor of
Answer: C. 4
Explanation: $R_{max}\propto P^{1/4}$ and $R_{max}\propto D$. $R_{max}\propto (16P)^{1/4}=2P^{1/4}$ and $R_{max}\propto D=2D$. Therefore, $R_{max}\propto 4P^{1/4}D$. The maximum range will increase by a factor of 4.
Topic: Optoelectronics
_____ current is the leakage current that flows through a photo diode with no input used in as light detectors.
Answer: B. Dark
Explanation: Detailed explanation not provided in the source.
Topic: Digital Circuits
The figure of merit of a logic family is given by
Answer: B. (propagation delay time) * (power dissipation)
Explanation: Detailed explanation not provided in the source.
Topic: Signals and Systems
_____ is defined as the time delay that a signal component of frequency ( ) undergoes as it passes from the input to output of the system.
Answer: A. Phase delay
Explanation: Detailed explanation not provided in the source.
Topic: Digital Circuits
Which statement is true regarding a behaviour modeling in VHDL?
Answer: A. There can be more than one process statement in an architecture which will interact concurrently.
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
The modulation index of an amplitude modulated wave is changed from 0 to 1. The transmitted power is
Answer: C. Increased by 50 percent
Explanation: Use the formula $P_{t}=P_{c}(1+\frac{m^{2}}{2})$. For $m=0$, $P_{t}=P_{c}$. For $m=1$, $P_{t}=P_{c}(1+\frac{1}{2}) = 1.5 P_{c}$. Hence, the transmitted power is increased by 50 percent.
Topic: Communication Systems
In a communication system, each message (1 or 0) is transmitted three times in order to reduce the probability of error. The detection is based on the majority rule at the receiver. If $P_{c}$ is the probability of bit error, the probability of error for this communication channel will be
Answer: A. $3P_{c}^{2}-2P_{c}^{3}$
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
For a satellite transponder with a receiver antenna gain of 12 dB, an LNA gain of 10 dB, and equivalent noise temperature of 26 $dBK^{-1}$, the $G/Te$ is
Answer: B. $-4~dBK^{-1}$
Explanation: The total gain $G$ is the sum of antenna gain and LNA gain in dB. $G = 12 + 10 = 22~dB$. $\frac{G}{T}=(G)_{dB}-T(dBK^{-1}) = (22-26)dBK^{-1} = -4~dBK^{-1}$.
Topic: Electronic Devices
The conductivity of the intrinsic germanium at $300^{\circ}K$ is
When $n_{i}$ at $300^{\circ}K=2.5\times10^{13}/cm^{3}$ and $\mu_{n}$ and $\mu_{p}$ in germanium are 3800 and 1800 $cm^{2}/Vs$ respectively.
Answer: B. 0.0224 S/cm
Explanation: $\sigma=(n\mu_{n}+p~\mu_{p})q$. For intrinsic semiconductor $\sigma=(\mu_{n}+\mu_{p})n_{i}q$, where $n=p=n_{i}$. Therefore, $\sigma = (3800+1800)\times2.5\times10^{13}\times1.6\times10^{-19} = 0.0224~S/cm$.
Topic: Analog Circuits
As compared to a full wave rectifier using 2 diodes, the four diode bridge rectifier has the dominant advantage of
Answer: B. Lower peak inverse requirement
Explanation: Detailed explanation not provided in the source.
Topic: Computer Organization
In a real time system, the simplest scheme that allows the operating system to allocate memory to two processes simultaneously is
Answer: B. Pipeline
Explanation: Detailed explanation not provided in the source.
Topic: Mathematics
$(cos~5\theta-i~sin~5\theta)^{2}$ is same as
Answer: C. $(cos\theta+i~sin~\theta)^{-10}$
Explanation: Detailed explanation not provided in the source.
Topic: Computer Organization
The process of imitating one system with another so that the imitating systems accepts the same data, executes same programs and achieves same results as the imitated systems is known as
Answer: D. Emulation
Explanation: Detailed explanation not provided in the source.
Topic: Network Theory
The values of R, L and C in series RLC circuit that resonates at 1.5 kHz and consumes 50 W from a 50 V ac source operating at the resonant frequency. The bandwidth is 0.75 kHz.
Answer: A. $R=50~ohm$, $L=10.6~mH$, $C=1.06~\mu F.$
Explanation: At resonance RLC circuit impedance is resistive. $R=\frac{V^{2}}{P}=\frac{50\times50}{50}=50~\Omega$. For series RLC circuit, $B.W.=\frac{R}{2\pi L} \Rightarrow L=\frac{R}{2\pi\times B.W.} = \frac{50}{2\pi\times0.75\times10^{3}}=10.6~mH$. Also, $f_{0}=\frac{1}{2\pi\sqrt{LC}} \Rightarrow (f_{0})^{2}=\frac{1}{4\pi^{2}LC} \Rightarrow C=\frac{1}{4\pi^{2}\times L\times(f_{0})^{2}} = \frac{1}{4\pi^{2}\times10.6\times10^{-3}\times(1.5\times10^{3})^{2}} = 1.06~\mu F$.
Topic: Electromagnetics
When VSWR is 3, the magnitude of the reflection co-efficient will be
Answer: C. $1/2$
Explanation: Magnitude of reflection coefficient $|\Gamma| = \frac{VSWR-1}{VSWR+1} = \frac{3-1}{3+1}=\frac{2}{4}=\frac{1}{2}$.
Topic: Digital Circuits
If a counter having 10 FFs is initially at 0, what count will it hold after 2060 pulses?
Answer: A. 000 000 1100
Explanation: Detailed explanation not provided in the source.
Topic: Signals and Systems
The output of a circular convolution performed on two signals $x_{1}(n)=\{\underline{2},1,2,1\}$ and $x_{2}(n)=\{\underline{1},2,3,4\}$ is
Answer: B. (14, 16, 14, 16)
Explanation: Using matrix multiplication after shifting, the circular convolution yields (14, 16, 14, 16).
Topic: Digital Circuits
When using a sequential code to design a combinational logic in VHDL, if complete truth table is not defined, the synthesis tool will implement a _____ which is not required
Answer: A. Clock buffer
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
In case of which of the following an increase on the modulation index leads to increase in bandwidth
Answer: D. Both (a) and (b)
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
Four voice signals each limited to 4 kHz and sampled at Nyquist rate, are converted into binary PCM signal using 256 quantization levels. The bit transmission rate for the time division multiplexing signal will be
Answer: C. 256 kbps
Explanation: $Rate=n\cdot N\cdot f_{s}$. Here $n=4$ signals. $N = \log_{2}(256) = 8$ bits. $f_{s} = 2 \times 4 \text{ kHz} = 8 \text{ kHz}$. $Rate = 4 \times 8 \times 8 \text{ kbps} = 256 \text{ kbps}$.
Topic: Electromagnetics
A wave guide section in a microwave circuit will act as a
Answer: C. High pass filter
Explanation: Detailed explanation not provided in the source.
Topic: Analog Circuits
A 24 V, 600 mW Zener is to be used for providing a 24 V stabilized supply to a variable load. Assume that for proper Zener action, a minimum of 10 mA must flow through the Zener. If the input voltage is 32 V, what would be the value of R and the maximum load current?
Answer: D. 320 ohm, 15 mA
Explanation: When $V_{z}=24V$, $P_{z}=600~mW$, $I_{zk}=10~mA$. $I_{zmax}=\frac{P_{zmax}}{V_{z}}=\frac{600~mW}{24~V}=25~mA$. When $I_{zmax}$ occurs, no current flows through $R_{L}$ i.e. $R_{L}$ is open circuited. $25~mA=\frac{32-24}{R} \Rightarrow R=\frac{8~V}{25mA}=320~\Omega$. Current from source $I=\frac{32-24}{320}=25mA$. Maximum load current $I_{Lmax}=I-I_{zk} = 25~mA-10~mA=15~mA$.
Topic: Mathematics
The value of x at which y has a minimum for $y=x^{2}-3x+1$ is
Answer: B. $3/2$
Explanation: $y=x^{2}-3x+1$. $\frac{dy}{dx}=2x-3=0 \Rightarrow x=\frac{3}{2}$. $\frac{d^{2}y}{dx^{2}}=2>0$. So, at $x=\frac{3}{2}$, y has minimum value.
Topic: Data Structures
In what order the elements of a pushdown stack are accessed?
Answer: C. Last In First Out (LIFO)
Explanation: Detailed explanation not provided in the source.
Topic: Network Theory
What is the value of C such that equivalent capacitance across X-Y is 5 F?
Answer: D. 21 F
Explanation: By applying star to delta conversion repeatedly as shown in the source diagrams, the network simplifies to an equivalent capacitance $C_{eq} = \frac{19}{8} + \frac{3C}{3+C}$. Setting $C_{eq} = 5$ F, we get $5 = \frac{19}{8} + \frac{3C}{3+C} \Rightarrow \frac{3C}{3+C} = 2.625 \Rightarrow 3C = 7.875 + 2.625C \Rightarrow 0.375C = 7.875 \Rightarrow C = 21 F$.
Topic: Optoelectronics
For a 3-$\mu m$ diameter optical fiber with core and cladding indexes of refraction of 1.545 and 1.510, respectively. The cut-off wavelength is
Answer: B. $1.29~\mu m$
Explanation: $\lambda_{c}=\frac{2\pi a n_{1}}{V_{c}}(2\Delta)^{1/2}$ where $V_{c}=2.405$ (constant), $a=$ radius of optical fiber ($1.5~\mu m$), $n_{1}=$ core refractive index (1.545). $\Delta=1-\frac{n_{2}}{n_{1}}=0.022$. $\lambda_{c}=\frac{2\pi\times1.5\times10^{-6}\times1.545}{2.405}\times(2\times0.022)^{1/2} = 1.28\times10^{-6}m=1.28~\mu m$.
Topic: Digital Circuits
A 12-bit ADC is operating with a 1 $\mu s$ clock period and total conversion time is seen to be 14 $\mu s$ always. The ADC must be of the type
Answer: D. Successive approximation type
Explanation: Repeated in previous year. (Successive approximation ADCs typically require a fixed number of clock cycles proportional to the number of bits, roughly $n$ to $n+2$ cycles).
Topic: Signals and Systems
Consider the analog signal $x(t)=3~cos~100\pi t$. If the signal is sampled at 200 Hz, the discrete time signal obtained will be
Answer: B. $3~cos(\pi n/2)$
Explanation: $f_{s}=200~Hz$, $T_{s}=\frac{1}{200}sec$. $x(nT_{s})=3~cos(100\pi \cdot \frac{n}{200}) = 3~cos(\frac{\pi n}{2})$.
Topic: Digital Circuits
In VHDL all the statements written inside a process statement are
Answer: C. Both (a) and (b)
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
In an amplitude modulated system if the total power is 600 W and the power in the carrier is 400 W, the modulation index is
Answer: D. 1
Explanation: $P_{t}=P_{c}(1+\frac{m^{2}}{2}) \Rightarrow 600=400(1+\frac{m^{2}}{2}) \Rightarrow 1+\frac{m^{2}}{2}=\frac{3}{2} \Rightarrow \frac{m^{2}}{2}=\frac{1}{2} \Rightarrow m^{2}=1 \Rightarrow m=1$.
Topic: Communication Systems
The channel capacity under the Gaussian noise environment for a discrete memoryless channel with a bandwidth of 4 MHz and SNR of 31 is
Answer: A. 20 Mbps
Explanation: According to Shannon's channel capacity theorem: $C=B~\log_{2}(1+SNR) = 4\times 10^6 \times \log_{2}(1+31) = 4~\log_{2}32 = 4\times5~\text{Mbps} = 20~\text{Mbps}$.
Topic: Communication Systems
In satellite communication frequency modulation is used because satellite channel has
Answer: C. Large bandwidth and severe noise
Explanation: Detailed explanation not provided in the source.
Topic: Electronic Devices
A PN junction in series with a 100 ohm resistor is forward biased so that a current of 100 mA flows. If voltage across the combination is instantaneously reversed to 10 V at time $t=0$, the reverse current that flows through the junction at $t=0$ is approximately given by
Answer: D. 100 mA
Explanation: At $t=0$, still that diode in forward biased but polarity of voltage source is changed, so that current is same in magnitude because of stored charge but in reverse direction. Hence at $t=0$ Reverse recovery current = 100 mA.
Topic: Analog Circuits
Ripple factor for a half wave rectifier is
Answer: D. 1.21
Explanation: Detailed explanation not provided in the source.
Topic: Computer Organization
_____ is a primitive that can execute code. It contains an instruction pointer (= program counter) and sometimes has its own stack.
Answer: D. Thread
Explanation: A thread is the primitive that can execute code. It contains an instruction pointer (= program counter) and some times has its own stack.
Topic: Mathematics
If $\alpha$ and $\beta$ are the roots of the equation $x^{2}-px+q=0$, then $\Sigma\alpha^{2}$ is
Answer: C. $p^{2}-2q$
Explanation: $x^{2}-px+q=0$. $\alpha^{2}+\beta^{2}=(\alpha+\beta)^{2}-2\alpha\beta = p^{2}-2q$.
Topic: Microprocessors
A microprocessor with 12-bit address bus will be able to access _____ kilobytes of memory.
Answer: D. 4
Explanation: $Size=2^{A}=2^{12}=4096 \text{ bytes} = 4$ kilobytes where, A = number of address lines.
Topic: Network Theory
A practical current source is usually represented by
Answer: B. A resistance in parallel with an ideal current source.
Explanation: Detailed explanation not provided in the source.
Topic: Electromagnetics
The dominant mode in a rectangular wave guide is $TE_{10}$ because this mode has
Answer: D. The highest cut-off wavelength
Explanation: Detailed explanation not provided in the source.
Topic: Optoelectronics
The critical angle $\theta_{c}$ in an optical fiber is given by
Where $n_{1}$ is refractive index of medium 1 and $n_{2}$ is the refractive index of medium 2.
Answer: A. $sin^{-1}(n_{2}/n_{1})$
Explanation: Detailed explanation not provided in the source.
Topic: Digital Circuits
In a JK flip-flop we have $J=Q'$ and $K=1$. Assuming that the flip-flop was initially cleared and clocked for 6 pulses, the sequence at the Q output will be
Answer: D. 010101
Explanation: Detailed explanation not provided in the source.
Topic: Signals and Systems
Which of the following system is linear?
Answer: C. $y(n)=x(n^{2})$
Explanation: Detailed explanation not provided in the source.
Topic: Digital Circuits
Which of the following operator cannot be synthesized by VHDL synthesis tools?
Answer: C. *
Explanation: No option is right. These all operators are used in VHDL (+ Addition, - Subtraction, * Multiplication, & Concatenation). Note: The source key indicates an error in the question options.
Topic: Communication Systems
A signal $m_{1}(t)$ is band limited to 3.6 kHz and the three other signals $m_{2}(t)$, $m_{3}(t)$ and $m_{4}(t)$ are band limited to 1.2 kHz each, and these signals are transmitted by means of TDM. Then, what will be the transmission bandwidth of the channel?
Answer: A. 7.2 kHz
Explanation: $B.W.=R_{b}/2 = \frac{(3.6+1.2\times3)\times2}{2}=7.2~kHz$.
Topic: Communication Systems
For a 10 bit PCM system the signal to quantisation noise ratio is 62 dB. If the number of bits is increased by 2, then the signal to quantisation noise ratio will
Answer: B. Increase by 12 dB
Explanation: $SN_{q}R=1.8+6n$. Increasing $n$ by 2 will increase the signal to quantization noise ratio by $6 \times 2 = 12~dB$.
Topic: Communication Systems
The modulation normally used with the digital data is
Answer: D. QPSK
Explanation: Detailed explanation not provided in the source.
Topic: Electronic Devices
For the 2N338 transistor, the manufacturer specifies $P_{max}=100~mW$ at $25^{\circ}C$ free air temperature and the maximum junction temperature $T_{j~max}=125^{\circ}C$. Its thermal resistance is
Answer: C. $1000^{\circ}C/W$
Explanation: $(T_{j}-T_{A})=\theta P_{c,max} \Rightarrow (125-25)=\theta\times100~mW \Rightarrow \theta=1000^{\circ}C/W$.
Topic: Analog Circuits
In a Class AB amplifier, the current flows through the active device for
Answer: C. More than half but less than full cycle
Explanation: Detailed explanation not provided in the source.
Topic: Computer Organization
Which of the following is not true regarding a preemptive kernel?
Answer: C. The executing thread is never interrupted
Explanation: Detailed explanation not provided in the source.
Topic: Mathematics
The solution of differential equation $dy/dx=e^{x-y}+x^{2}e^{-y}$ is
Answer: A. $e^{y}=e^{x}+x^{3}/3+c$
Explanation: $\frac{dy}{dx}=e^{x-y}+x^{2}e^{-y} \Rightarrow \frac{dy}{dx}=\frac{e^{x}+x^{2}}{e^{y}} \Rightarrow e^{y}dy=(e^{x}+x^{2})dx$. Integrating both sides, $\int e^{y}dy=\int e^{x}dx+\int x^{2}dx \Rightarrow e^{y}=e^{x}+\frac{x^{3}}{3}+c$.
Topic: Microprocessors
Which of the following statements with reference to a generic microprocessor is correct?
Answer: C. Machine cycle time period is shorter than instruction cycle time period
Explanation: Detailed explanation not provided in the source.
Topic: Network Theory
An electric iron designed for 110 V AC supply was rated at 500 W. It was put across a 220 V supply. Assuming that at 110 V it supplied 500 W output (i.e. no losses) at the new voltage will supply
Answer: D. 2000 W
Explanation: Practically electric iron should be damaged. But as option we can calculate ideally as $R=\frac{V^{2}}{P}=\frac{110\times110}{500}=24.2~\Omega$. $P_{new}=\frac{V^{2}}{R}=\frac{220\times220}{24.2} \text{ Watt} = 2000~W$.
Topic: Electromagnetics
A very lossy, $1/4$ long, 50 ohm transmission line is open circuited at the load end. The input impedance measured at the other end of the line is approximately.
Answer: A. 0
Explanation: $Z_{in}=\frac{Z_{0}^{2}}{Z_{L}}=\frac{Z_{0}^{2}}{\infty}=0$.
Topic: Optoelectronics
For a single mode optical cable with $0.25~dB/km$ loss, the optical power 100 km from a 0.1 mW source will be
Answer: B. -35 dBm
Explanation: Power input $= -10~dBm$ (since $0.1~mW = 10 \log_{10}(0.1) = -10~dBm$). Path loss $(L_{p})=0.25\frac{dBm}{km}\times100~km = 25~dB$. Power output $=-10-25=-35~dBm$.
Topic: Digital Circuits
The function of a strobe function in digital system is
Answer: A. to reset memory register
Explanation: Detailed explanation not provided in the source.
Topic: Signals and Systems
The impulse response of a linear time invariant system is $h(n)=\{1,\underline{2},1,-1\}$. The response for the input signal $x(n)=\{1,2,3,1\}$ is
Answer: C. {1, 4, 8, 8, 3, -2, -1}
Explanation: Using convolution sum method (matrix/tabular multiplication), $x(n)*h(n)=\{1,4,8,8,3,-2,-1\}$.
Topic: Digital Circuits
Which of the following statement regarding a constant is not true?
Answer: B. The value of constant can be changed with in the design description
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
The intermediate frequency of a super-heterodyne receiver is 450 KHz. If it is tuned to 1200 KHz, the image frequency will be
Answer: D. 2100 KHz
Explanation: $f_{image}=f_{s}+2f_{IF} = 1200+2\times450 = (1200+900)kHz=2100kHz$.
Topic: Communication Systems
The bandwidth of a 'N' bit binary coded PCM signal for modulating a signal having bandwidth of 'f' Hz is
Answer: C. Nf Hz
Explanation: Detailed explanation not provided in the source.
Topic: Communication Systems
Geostationary satellites are placed in equatorial orbits at the height approximately
Answer: D. 36000 km
Explanation: Detailed explanation not provided in the source.
Topic: Electronic Devices
An NPN transistor has a beta cut-off frequency $f_{\beta}$ of 1 MHz, and a common emitter short circuit low frequency current gain $\beta_{0}$ of 200, its unity gain frequency $f_{T}$ and the alpha cut-off frequency $f_{\alpha}$ respectively are
Answer: A. 200 MHz, 201 MHz
Explanation: $f_{T}=f_{\beta}\cdot\beta=(1\times200)MHz=200MHz$. $f_{\alpha}=\frac{f_{T}}{\alpha}=\frac{200}{0.99}=201MHz$ (since $\alpha = \beta/(1+\beta) = 200/201 \approx 0.995$).
Topic: Analog Circuits
For a class B amplifier providing a 20 V peak signal to 16 ohm load and a power supply of $V_{cc}=30$ V, the efficiency will be
Answer: A. 52.3%
Explanation: A 20-V peak signal across a 16-$\Omega$ load provides a peak load current of $I_{L}(P)=\frac{V_{L}(P)}{R_{L}}=\frac{20~V}{16~\Omega}=1.25~A$. $I_{dc}=\frac{2}{\pi}I_{L}(P)=\frac{2}{\pi}(1.25)=0.796~A$. $P_{i}(dc)=V_{cc}I_{dc}=(30V)(0.796A)=23.9W$. $P_{0}(ac)=\frac{V_{L}^{2}(P)}{2 R_{L}}=\frac{(20~V)^{2}}{2(16~\Omega)}=12.5~W$. $\%\eta=\frac{P_{0}(ac)}{P_{i}(dc)}\times100\% = \frac{12.5~W}{23.9~W}\times100\%=52.3\%$.
Topic: Microprocessors
When a microprocessor interfaces with a peripheral or memory device, the normal timing of the microprocessor may need to be altered by introducing
Answer: B. Wait states
Explanation: Detailed explanation not provided in the source.
Topic: Mathematics
$\int_{0}^{\pi/2}(cos^{3}x)dx=$
Answer: B. $2/3$
Explanation: $\int_{0}^{\pi/2}cos^{3}x~dx=\int_{0}^{\pi/2}sin^{3}x~dx=\frac{2}{3\cdot 1}=\frac{2}{3}$.
Topic: Microprocessors
In a 8085 microprocessor system with memory mapped I/O
Answer: D. Arithmetic and logic operations can be directly performed with I/O data.
Explanation: Detailed explanation not provided in the source.
Topic: Network Theory
The Thevenin and Norton circuits are
Answer: A. Single frequency equivalent circuits
Explanation: Detailed explanation not provided in the source.
Topic: Electromagnetics
A broadside array operating at 100 cm wavelength consist of 4 half wave dipoles spaced 50 cm apart. Each element carries radio frequency current in the same phase and of magnitude 0.5 A. The radiated power will be _____ if the radiation resistance is 146 ohm.
Answer: A. 146 W
Explanation: $P_{rad}=n\times I_{rms}^{2}\times R = 4\times(\frac{1}{2})^{2}\times146=146~W$.