Sample Exam 4 – Radio Society of Sri Lanka

Fundamentals of Electricity & Radio Communications sample paper-4

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The Radio Society of Sri Lanka

The copy right of the information contained in this sample exam are with the Radio Society of Sri Lanka (RSSL).

These questions are mainly targeting the Radio Amateur exam for Novice and General class. The recommended time duration is 1 hour. For more information please contact Mr. Jayasiri Wijeratne (4S7VJ) 4s7vj@rssl.lk

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Congratulations - you have completed Fundamentals of Electricity & Radio Communications sample paper-4. You scored %%SCORE%% out of %%TOTAL%%. Your performance has been rated as %%RATING%%

Your answers are highlighted below.

Question 1

A sunspot cycle is

A	5 years
B	10 years
C	11 years
D	21 years

Question 2

The transformer is used to change the value of

A	voltage
B	none of these
C	power
D	frequency

Question 3

A 10 Ohm resistor consumes a current of 1 Ampere. The power dissipated in the resistor is

A	0.1 Watt
B	1 Watt
C	10 Watts
D	100 Watts

Question 4

A transformer is laminated to

A	reduce hysteresis losses
B	reduce eddy current losses
C	increase magnetic flux
D	increase exciting current

Question 5

If a person gets an electric shock you should immediately

A	Remove the victim to a safe place
B	Send for a doctor
C	Switch off the mains supply immediately
D	Give him artificial respiration

Question 6

The conductivity of a current carrying conductor can be decreased by

A	reducing its length
B	increasing its diameter
C	reducing its temperature
D	reducing its diameter

Question 7

The Radiation Resistance of a ½-wave dipole is

A	50 Ohms
B	100 Ohms
C	75 Ohms
D	300 Ohms

Question 8

The automatic gain control (AGC) circuit is usually used to control the gain of the

A	audio amplifier
B	IF amplifier
C	mixer
D	detector

Question 9

Radio waves above 30 kHz are called

A	Audio frequencies.
B	radio frequencies.
C	very high frequencies.
D	super high frequencies

Question 10

29.1MHz is the third harmonic of

A	19.4 MHz
B	87.3 MHz
C	90 MHz
D	9.7 MHz

Question 11

A dipole is used on 7 MHz will work very efficiently on

A	14 MHz
B	28 MHz
C	21 MHz
D	3.5 MHz

Question 12

A fuse is used in an electrical circuit

A	to prevent damage of all equipment due to overload
B	to protect from lightning
C	none of these
D	to prevent AC hum

Question 13

What happens to the input impedance of a Yagi antenna when more elements are added ?

A	remains unchanged
B	Decreases
C	will cause unbalanced
D	increases

Question 14

The total power content of an amplitude modulated signal is 10W, and the percentage modulation is 100%. The power transmitted by the side bands is

A	3.33 W
B	5 W
C	6.67 W
D	10 W

Question 15

The Meggar is used for

A	measuring power
B	measuring current
C	measuring voltage
D	testing insulation

Question 16

What is the total inductance between A and B ?

A	27 mH
B	18 mH
C	1 mH
D	9 mH

Question 17

The resonance frequency of a tuned (LRC) series circuit is given by

A	1 / 2π√(LC)
B	2π/√(LC)
C	(1 / 2π)√(L/C)
D	1 / [2π√(LC)]

Question 17 Explanation:

The correct answer is 1 / [2π√(LC)] ; but 1 / 2π√(LC) is confused whether it is equal to 1 / [2π√(LC)] or [1 / 2] π√(LC)

Question 18

Which one is incorrect from following statments

A	Power factor of a pure resistor is 1
B	Power factor = actual power / apperent power
C	Power factor of a pure inductor is zero
D	Power factor of a capacitor is infinity

Question 19

The basic concept of Amplitude Modulation (AM) is to vary the

A	amplitude of carrier signal
B	frequency of modulating signal
C	amplitude of modulating signal
D	frequency of carrier signal

Question 20

The value of the resistor shown in the figure is

A	21Ω
B	210Ω
C	12Ω
D	120Ω

Question 21

A coaxial cable is

A	a balanced line
B	none of these
C	an unbalanced line
D	a wave guide

Question 22

A vertical polarized transmission could have for best reception

A	a cross polarized antenna
B	a circular polarized antenna
C	A horizontal receiving antenna
D	a vertical receiving antenna

Question 23

An antenna whose input impedance is 50Ω Should have a feeder link with an impedance of

A	300 Ω
B	100 Ω
C	75 Ω
D	50 Ω

Question 24

One way communication is called

A	half duplex
B	duplex
C	monocom
D	simplex

Question 25

The deviation of a standard 2 meter Amateur Radio Transmitter is

A	25 kHz
B	50 kHz
C	5kHz
D	2.5 kHz

Question 26

The ability of a receiver to pickup weak signal is

A	sensitivity
B	none of these
C	stability
D	selectivity

Question 27

A 300 Ohm twin feeder line is

A	an unbalanced line
B	none of the above
C	a balanced line
D	a wave guide

Question 28

Envelope of diode detector is used for the detection of

A	CW signals
B	SSB signals
C	AM signals
D	FM signals

Question 29

To determine the voltage polarity across a resistor, we should know

A	the direction of the current
B	the battery voltage
C	the magnitude of the current
D	the value of the resistor

Question 30

How can key clicks be eliminated?

A	Have an antenna matching device.
B	Neutralize the P.A.
C	Use a key click filter
D	Should have a regulated power supply

Question 31

The equivalent resistance of the circuit given is

A	11 kΩ
B	22 kΩ
C	10 kΩ
D	1 kΩ

Question 32

20 dB power gain is an increase power by

A	2 times
B	20 times
C	10 times
D	100 times

Question 33

The purpose of adding reflector and directors to a folded dipole antenna is

A	to have some effect on its impedance
B	to decrease its impedance
C	to increase its impedance
D	none of these

Question 34

Over modulation in an F.M. transmission will cause

A	to occupy wide bandwidth
B	Heavy distortion
C	To occupy narrow bandwidth
D	none of the above

Question 35

An R.F. choke

A	prevent AC ripple.
B	prevent the flow of R.F. current
C	Aids the flow of R.F. current
D	accelerates the flow of R.F.

Question 36

The electric field of an antenna is parallel to the Earth’s surface. The polarization of the antenna is

A	none of these
B	horizontal
C	vertical
D	circular

Question 37

A moving coil meter responds only by itself to

A	AC
B	AC+DC
C	DC
D	Frequency

Question 38

The power input of a transistor is

A	collector current X emitter current
B	base current X collector voltage
C	Emitter current x base current
D	collector current X collector voltage

Question 39

What is the effective capacitance between the points A and B shown in the diagram ?

A	9pF
B	27 pF
C	1 pF
D	18 pF

Question 40

The unit of electric current is

A	Volt
B	Ampere
C	Ampere hour
D	Hertz

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