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 deviation of a standard 2 meter Amateur Radio Transmitter is

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

Question 2

One way communication is called

A	duplex
B	half duplex
C	monocom
D	simplex

Question 3

The unit of electric current is

A	Hertz
B	Ampere
C	Volt
D	Ampere hour

Question 4

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 5

The value of the resistor shown in the figure is

A	12Ω
B	120Ω
C	21Ω
D	210Ω

Question 6

How can key clicks be eliminated?

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

Question 7

A coaxial cable is

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

Question 8

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

A	vertical
B	none of these
C	circular
D	horizontal

Question 9

The equivalent resistance of the circuit given is

A	11 kΩ
B	10 kΩ
C	22 kΩ
D	1 kΩ

Question 10

20 dB power gain is an increase power by

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

Question 11

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

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

Question 12

Which one is incorrect from following statments

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

Question 13

The Radiation Resistance of a ½-wave dipole is

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

Question 14

The Meggar is used for

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

Question 15

Radio waves above 30 kHz are called

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

Question 16

A sunspot cycle is

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

Question 17

A fuse is used in an electrical circuit

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

Question 18

The conductivity of a current carrying conductor can be decreased by

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

Question 19

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

A	audio amplifier
B	IF amplifier
C	detector
D	mixer

Question 20

The power input of a transistor is

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

Question 21

If a person gets an electric shock you should immediately

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

Question 22

The ability of a receiver to pickup weak signal is

A	stability
B	selectivity
C	sensitivity
D	none of these

Question 23

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

A	will cause unbalanced
B	Decreases
C	remains unchanged
D	increases

Question 24

29.1MHz is the third harmonic of

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

Question 25

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

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

Question 26

The transformer is used to change the value of

A	frequency
B	none of these
C	voltage
D	power

Question 27

Over modulation in an F.M. transmission will cause

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

Question 28

A transformer is laminated to

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

Question 29

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

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

Question 29 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 30

An R.F. choke

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

Question 31

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

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

Question 32

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

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

Question 33

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

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

Question 34

A 300 Ohm twin feeder line is

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

Question 35

Envelope of diode detector is used for the detection of

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

Question 36

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

A	75 Ω
B	50 Ω
C	100 Ω
D	300 Ω

Question 37

A vertical polarized transmission could have for best reception

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

Question 38

A moving coil meter responds only by itself to

A	AC
B	Frequency
C	DC
D	AC+DC

Question 39

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	5 W
B	10 W
C	3.33 W
D	6.67 W

Question 40

What is the total inductance between A and B ?

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

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