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# Multiple choice question for engineering

## Set 1

1. Copper behaves as a
a) Conductor always
b) Conductor or dielectric depending on the applied electric field strength
c) Conductor or dielectric depending on the frequency
d) Conductor or dielectric depending on the electric current density

Answer: a [Reason:] The loss tangent for copper is very large due to its high conductivity. This shows that the copper behaves as a conductor in all conditions.

2. In a good conductor the phase relation between the tangential components of electric E and the magnetic field H is as follows
a) E and H are in phase
b) E and H are out of phase
c) H leads E by 90
d) E leads H by 45

Answer: d [Reason:] In a conductor, the intrinsic impedance gives the phase relation between E and H. For a conductor, the electric field and magnetic field are in 45 degree phase difference. E and H are 45 leading.

3. For an electromagnetic wave incident from one medium to a second medium, total internal reflection takes place when
a) Angle of incidence is equal to the Brewster angle with E field perpendicular to the plane of incidence
b) Angle of incidence is equal to the Brewster angle with E field parallel to the plane of incidence
c) Angle of incidence is equal to the critical angle with the wave moving from the denser to rarer medium
d) Angle of incidence is equal to the critical angle with the wave moving from the rarer to denser medium

Answer: c [Reason:] Total internal reflection takes place when the angle of incidence is greater than the critical angle. Also the wave should move from the denser medium to a rarer medium.

4. For maximum power transfer, a lossless transmission line 50 ohm is to be matched to a resistive load impedance of 100 ohm. The characteristic impedance of the wavelength/4 transformer is
a) 70.7
b) 50
c) 100
d) Infinity

Answer: a [Reason:] For maximum power transfer, Zin = Z02/ZL. On substituting for the given values, we get the characteristic impedance as 70.7 ohm.

5. In an impedance Smith chart , a clockwise movement along a constant resistance circle gives rise to
a) Decrease in reactance
b) Increase in reactance
c) No change in reactance
d) No change in impedance

Answer: b [Reason:] In clockwise direction, along the constant resistance circle gives rise to an increase in the value of reactance.

6. A transmission line is distortionless if
a) RL = 1/GC
b) RL = GC
c) LG = RC
d) RG = LC

Answer: c [Reason:] Condition for distortionless line is R/L = G/C. In other words, the rise time constant is equal to the fall time constant. Hence RC = LG.

7. A lossless line having 50 ohm characteristic impedance and length wavelength/4 is short circuited at one end connected to an ideal voltage source of 1V at the other end. The current drawn from the voltage sources is
a) 0
b) 0.02
c) Infinity
d) 50

Answer: a [Reason:] For a quarter wave transformer, the input impedance is given by Zin = Z02/ZL. The load impedance will be zero in case of short circuit. Thus the input impedance will be infinite. The current drawn is I = V/ZL = 1/∞ = 0.

8. The capacitance per unit length and the characteristic impedance of a lossless transmission line are C and Z respectively. The velocity of a travelling wave on the transmission line is
a) ZC
b) 1/ZC
c) Z/C
d) C/Z

Answer: b [Reason:] The characteristic impedance of the Z = √(L/C) and the velocity of propagation is V = 1/√(LC). Thus we get V = 1/ZC.

9. The minimum distance of the stub from the load side is 5 cm. Calculate the guided wavelength of the transmission line.
a) 5 cm
b) 2.5 cm
c) 10 cm
d) 1.25 cm

Answer: c [Reason:] The minimum distance of the stub from the load line is given by Vmin = wavelength/2. On substituting the given value, we get the guided wavelength as 10 cm.

10. One end of a lossless transmission line having the characteristic impedance of 75 ohm and length of 1 cm is short circuited. At 3 GHz, the input impedance at the other end of the transmission line is
a) 0
b) Resistive
c) Inductive
d) Capacitive

Answer: d [Reason:] The input impedance is given by ZIN = j Zo tan 2pi l/wavelength. For short circuited line, ZL = 0. On substituting the given values we get the input impedance as j54.49 ohm.

## Set 2

1. The tangential component of an electric field will be continuous in which boundary?
a) Conductor-Conductor
b) Conductor-Dielectric
c) Dielectric-Dielectric
d) Any boundary

Answer: d [Reason:] The tangential component of an electric field will be continuous in any type of boundary.

2. The depth of penetration of a wave in a lossy dielectric increases with increasing
a) Conductivity
b) Permeability
c) Wavelength
d) Permittivity

Answer: c [Reason:] The depth of penetration or skin depth is inversely proportional to the frequency. Thus it has to be directly proportional to the wavelength.

3. Magnetic vector potential is a vector
a) Whose curl is equal to the magnetic flux density
b) Whose curl is equal to the electric field intensity
c) Whose divergence is equal to electric potential
d) Which is equal to the vector product E x H

Answer: a [Reason:] The magnetic vector potential is A. The curl of A is a vector and it is equal to the magnetic flux density. It is given by Curl(A) = B.

4. For the wave equation E = 10sin (wt-5z)ax, the wave propagation will be in the direction of
a) Y direction
b) Z direction
c) X direction
d) XY direction

Answer: b [Reason:] The equation represents the electric field component of the wave. Here, ax represents the electric wave direction and z represents the wave direction.

5. An electric field on a plane is described by its potential V = 20(r-1 + r-2), where r is the distance from the source. The field is due to
a) A monopole
b) A dipole
c) Both a monopole and a dipole

Answer: c [Reason:] In the potential given, one component is inversely proportional to r, which is due to a monopole and the other component is inversely proportional to r2, which is due to a dipole.

6. The electric field strength at a far-off point P due to a point charge, +q located at the origin O is 100 milliVolt/meter. The point charge is now enclosed by a perfectly conducting hollow metal sphere with its centre and the origin O. The electric field strength at the point, P is
a) Remains unchanged in its magnitude and direction
b) Remains unchanged in its magnitude but reverse in direction
c) Would be that due to a dipole formed by the charge, +q, at O and -q induced
d) Would be zero

Answer: d [Reason:] According to Gauss Law, the total displacement or electric flux through any closed surface surrounding charges is equal to the amount of charge enclosed. The total enclosed charge is -q + q = 0. Thus the flux and electric field strength will be zero.

7. The electric field of a uniform plane electromagnetic wve in free space, along the positive direction, is given by E = 10(ay + jaz)e-j25x. The frequency and polarization of the wave, respectively are
a) 1.2 GHz, left circular
b) 4 GHz, left circular
c) 1.2 GHz, right circular
d) 4 GHz, right circular

Answer: a [Reason:] The amplitudes of the components are the same. Hence it is circular polarization. The phase difference is +90 degree. Thus it is left hand circular polarisation. The frequency f = c/wavelength = 3 x 108 x 25/2 x 3.14= 1.2 GHz.

8. Identify which one of the following will NOT satisfy the wave equation.
a) 50ej(wt – 3z)
b) sin(w(10z + 5t))
c) cos(y2 + 5t)
d) sin x cos t

Answer: c [Reason:] The wave cos(y2 + 5t) does not satisfy the general wave equation. Thus it is not an electromagnetic wave.

9. The intrinsic impedance of copper at high frequencies is
a) Purely resistive
b) Purely inductive
c) Complex with a capacitive component
d) Complex with a inductive component

Answer: d [Reason:] The intrinsic impedance is given by √(jwµ√ϭ + jw€). Since copper is a good conductor, ϭ << jw€, thus the intrinsic impedance will have +j component only. This refers to complex with an inductive component.

10. A loop is rotating about the y axis in a magnetic field B = Bocos(wt + α)at. The voltage in the loop is
a) Zero
b) Due to rotation only
c) Due to transformer action only
d) Due to both rotation and transformer action

Answer: d [Reason:] The voltage in the loop is due to two reactions – time varying magnetic field and voltage induced in a loop moving with velocity v in steady magnetic field. Thus the voltage in the loop is due to both rotation and transformer action.

## Set 3

1. What are the factors of filters which are determined by the speed of the operation in a digital signal processor?
a) attenuation constant
b) frequency
c) bandwidth
d) phase

Answer: c [Reason:] The bandwidth of any filter depends on the speed of operations held in a digital signal processor.

2. How many tables does an FIR function of a digital signal processor possess?
a) 1
b) 2
c) 3
d) 4

Answer: b [Reason:] Digital signal processor function involves setting up of two tables and one is for sampled data and the other table is for filter coefficients which determine the filter response. It takes values from the table and performs programs.

3. Why is said that branch prediction is not applicable in a digital signal processor?
a) low bandwidth
b) high bandwidth
c) low frequency
d) high frequency

Answer: a [Reason:] Loop control timing varies depending on the branch predictions which inturn make bandwidth predictions difficult thereby lowering the bandwidth of the digital signal processor.

4. Which architecture can one overcome the low bandwidth issue in MC6800 family?
a) RISC
b) CISC
c) von Neumann
d) program stored

Answer: a [Reason:] RISC architecture can offer some improvement in the low bandwidth issue since it has the ability to perform operations in a single cycle.

5. Which architecture in digital signal processor reduces the execution time?
a) Harvard
b) CISC
c) program storage
d) von Neumann

Answer: a [Reason:] Harvard architecture in a digital signal processor allows continuous data fetching and performing the corresponding instructions.

6. Which of the following processors also can work as a digital signal processor?
a) 8086
b) 8088
c) 8080
d) ARM9E

Answer: d [Reason:] ARM9E can also have DSP level of performance without having a digital signal processor by its enhanced DSP instructions.

7. What types of modules are used in the digital signal processor to form the loop structure?
a) modulo-timer
b) modulo-counter
c) timer
d) external timer

Answer: b [Reason:] By using hardware multipliers, counters etc the entire hardware can be redesigned to perform some specific functions which are used in digital signal processors. One such is the modulo-counter to form the loop structure.

8. Name a processor which is used in digital audio appliances.
a) 8086
b) Motorola DSP56000
c) 80486
d) 8087

Answer: b [Reason:] Motorola DSP56000 is a powerful digital signal processor which is used in digital audio applications which have the capability of noise reduction and multi-band graphics whereas 8087 is a coprocessor and 80486 and 8086 are microprocessors.

9. How many bit does DSP56000 processor have?
a) 8
b) 16
c) 24
d) 32

Answer: c [Reason:] In order to increase the resolution, DSP56000 is a 24-bit data word processor.

10. How many buses did DSP56000 possess?
a) 2
b) 3
c) 4
d) 5

Answer: b [Reason:] It possess three separate external buses, one is for the program and the remaining two buses are for X and Y memories for data.

11. Which of the following architecture does DSP56000 possess?
a) Harvard
b) von Neumann
c) CISC
d) program-stored

Answer: a [Reason:] DSP56000 possess Harvard architecture since this architecture has separate bus for program memory and data memory.

12. What does AAU stand for?
d) arithmetic access unit

Answer: b [Reason:] DSP56000 possess two external bus switches in which one is for data and the other is for the address for communicating with the outside world and these two switches are reproduced by the internal data bus and AAU.

13. How many address register does the AAU of a DSP56000 have?
a) 8
b) 16
c) 24
d) 32

Answer: c [Reason:] AAU have 24 address registers in three banks of eight.

14. How many register does a DSP56000 have?
a) 4
b) 5
c) 7
d) 6

Answer: c [Reason:] DSP56000 have six 24-bit registers for controlling the loop counts,operating mode, stack manipulation and condition codes.

15. Which of the following bits are used for sign extension in DSP56000?
a) upper 8 bits of the stack pointer
b) lower 8 bits of the stack pointer
c) lower 8 bits of the program counter
d) upper 8 bits of the program counter

Answer: d [Reason:] The DSP56000 have a 24-bit program counter in which the upper 8 bits are only used for sign extension.

## Set 4

1. Which of the following is also known as implicit address?
c) 1D model
d) 2D model

Answer: b [Reason:] The single address model is also known as implicit model because the second address is implied and is not directly given, that is, the source address is not supplied.

2. Which address mode uses two addresses and two accesses to transfer the data between the peripheral and the memory?
b) 1D model
c) 2D model
d) 3D model

Answer: a [Reason:] The dual address mode supports two addresses and two accesses for transferring data between a peripheral or memory and another memory location.

3. Which of the following address mode uses a buffer to hold data temporarily?
a) 1D model
b) 2D model
d) 3D model

Answer: c [Reason:] The dual address mode supports two addresses and two accesses for transferring data between a peripheral or memory and another memory location, which also consumes two bus cycles and a buffer within the DMA controller to hold data temporarily.

4. Which of the following model can implement circular buffer?
b) 1D model
c) 2D model
d) 3D model

Answer: b [Reason:] The 1D model can implement a circular buffer which makes an automatic reset to bring the address back to the beginning.

5. Which of the following uses an address and a counter to define the sequence of addresses?
b) 2D model
c) 1D model
d) 3D model

Answer: c [Reason:] The 1D model of the DMA controller uses an address location and a counter to define the address sequence which are used during the DMA cycles.

6. Which of the following is used to calculate an offset to base address?
c) 1D model
d) 2D model

Answer: d [Reason:] An address stride is specified which can be used for calculating the offset to the base address at the terminal of count. This address stride is used in the 2D model of the DMA controller.

7. Which can provide an address stride?
c) 1D model
d) 2D model

Answer: d [Reason:] In the 2D model of the DMA controller, an address stride is specified which can be used for calculating the offset to the base address at the terminal of count.

8. How is the count register can be splitted?
a) 2
b) 3
c) 4
d) 5

Answer: a [Reason:] In the 2D model of the DMA controller, in addition to the address stride there is a count register which can be split into two, in which one register is used to specify the count for the block and the second register is used to define the total number of blocks or the bytes to be transferred.

9. Which of the following has the ability to change the stride automatically?
a) 1D model
b) 2D model
c) 3D model

Answer: c [Reason:] In the 3D model of the DMA controller, it have the ability to change the address stride automatically so that blocks of different sizes and stride can be created.

10. Which is used to prioritise multiple request?
c) arbitration
d) chaining

Answer: c [Reason:] The arbitration is used to provide priority for a multiple access. This uses a priority scheme which may offers fair priority to the one channel, or a high priority to the other channel and so on. Such condition is otherwise known as round-robin condition in which the priority is equally divided.

## Set 5

1. Which of the following is used to reset the device in 8250?
a) MR
b) DDIS
c) INTR
d) RCLK

Answer: a [Reason:] MR is the master reset pin which helps to reset the device and restore the internal registers.

2. Which provides an input clock for the receiver part of the UART 8250?
a) RD
b) RCLK
c) MR
d) DDIS

Answer: b [Reason:] RCLK provides an input clock for the receiver part of the UART. RD is the read signal. MR is the master reset pin and DDIS is used to control bus arbitration logic.

3. Which of the following is a general purpose I/O pin?
a) OUT1
b) RD
d) MR

Answer: a [Reason:] There are two general purpose I/O pin OUT1 and OUT2. OUT1 is set by the programming bit 2 of the MCR to a ‘1’ whereas OUT2 is set by the programming bit 3 of the MCR to ‘1’. These are active low pins in 8250.

4. Which of the following indicate the type of access that the CPU needs to perform?
a) MR
b) RD
d) RCLK

Answer: b [Reason:] RD and WR signals are indicating the type of access that the CPU needs to perform, that is, whether it is a read cycle or write cycle.

5. Which pins are used for additional DMA control?
a) RXRDY
b) RD
c) MR
d) INR

Answer: a [Reason:] The RXRDY and TXRDY are two active low pins which are used for additional DMA control. It can be used for DMA transfers to and from the read and write buffers.

6. Which of the following are not used within the IBM PC?
a) TXRDY
b) BAUDOUT
d) OUT2

Answer: a [Reason:] The CPU is responsible for moving data to and from the UART in the IBM PC, therefore it does not have TXRDY and RXRDY pins which are used for DMA accessing.

7. Which pins are used to connect an external crystal?
a) INR
c) XIN
d) SIN

Answer: c [Reason:] The XIN and XOUT pins are used to connect an external crystal. These pins can also connect external clock.

8. Which UART is used in MC680 by 0 design?
a) Intel 8250
b) 16450
c) 16550
d) MC68681

Answer: d [Reason:] The MC68681 is a standard UART developed by Motorola. It has been used in many MC680 by 0 designs.

9. Which of the following have large FIFO buffer?
a) 8253
b) 8250
c) 16550
d) 16450