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

The conductivity of a current carrying conductor can be decreased by

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

Question 2

A fuse is used in an electrical circuit

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

Question 3

One way communication is called

A	monocom
B	simplex
C	half duplex
D	duplex

Question 4

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

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

Question 5

The ability of a receiver to pickup weak signal is

A	stability
B	selectivity
C	none of these
D	sensitivity

Question 6

Envelope of diode detector is used for the detection of

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

Question 7

An R.F. choke

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

Question 8

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

A	circular
B	vertical
C	none of these
D	horizontal

Question 9

The power input of a transistor is

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

Question 10

The equivalent resistance of the circuit given is

A	11 kΩ
B	22 kΩ
C	10 kΩ
D	1 kΩ

Question 11

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

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

Question 12

How can key clicks be eliminated?

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

Question 13

A sunspot cycle is

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

Question 14

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

A	75 Ω
B	100 Ω
C	50 Ω
D	300 Ω

Question 15

The unit of electric current is

A	Hertz
B	Volt
C	Ampere
D	Ampere hour

Question 16

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

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

Question 17

A 300 Ohm twin feeder line is

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

Question 18

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

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

Question 19

29.1MHz is the third harmonic of

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

Question 20

If a person gets an electric shock you should immediately

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

Question 21

The transformer is used to change the value of

A	frequency
B	none of these
C	voltage
D	power

Question 22

A transformer is laminated to

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

Question 23

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

A	remains unchanged
B	increases
C	Decreases
D	will cause unbalanced

Question 24

The value of the resistor shown in the figure is

A	120Ω
B	21Ω
C	12Ω
D	210Ω

Question 25

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 26

20 dB power gain is an increase power by

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

Question 27

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

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

Question 27 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 28

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

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

Question 29

Which one is incorrect from following statments

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

Question 30

A coaxial cable is

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

Question 31

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	6.67 W
B	5 W
C	3.33 W
D	10 W

Question 32

Radio waves above 30 kHz are called

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

Question 33

The Radiation Resistance of a ½-wave dipole is

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

Question 34

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

A	IF amplifier
B	audio amplifier
C	detector
D	mixer

Question 35

Over modulation in an F.M. transmission will cause

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

Question 36

The deviation of a standard 2 meter Amateur Radio Transmitter is

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

Question 37

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

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

Question 38

What is the total inductance between A and B ?

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

Question 39

A moving coil meter responds only by itself to

A	DC
B	AC
C	Frequency
D	AC+DC

Question 40

The Meggar is used for

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

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