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CBSE XII
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Physics
Physics
Electric charges and fields
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Communication systems
The TV transmission tower in Delhi has a height of $340\;m$ . The distance up to which the broad cost can received , (taking the radius of earth to be $6.4 \times 10^{6}m)$ is
cbse
class12
physics
ch15
sec-a
additional
medium
asked
Oct 3, 2016
by
meena.p
1
answer
Refractive index of ionosphere is
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
The electro magnetic waves of frequency $2\; MHz$ to $30\;MHz$ are used
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
Which of the following frequencies will be suitable for beyond the horizon communication ?
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
A radio station has two channels . One is AM at $1020\;KHz$ and the other FM at $89.5\;MHZ$ For good result you will use
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
LANDSAT series of satellite move in near polar orbits at an attitude of
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
The sky wave with a frequency of $50\;MHz$ is incident on D- region at an angle of $30^{\circ}$ then angle of refraction is
cbse
class12
physics
ch15
sec-a
additional
medium
asked
Oct 3, 2016
by
meena.p
1
answer
When radio waves passes through ionosphere , phase difference between space current and captive displacement current is .
cbse
class12
physics
ch15
sec-a
additional
medium
asked
Oct 3, 2016
by
meena.p
1
answer
Modem is a device which perform
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
Calculate the phase velocity of electro magnetic wave having electron density and frequency for D layer , $N = 400\; electron /cc, \nu = 300\;kHz$
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
The maximum range of ground or surface wave propagation depends on
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
Calculate the length of half wave dipole antenna at $300\;MHz$
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
A 400 watt carrier is modulated to a depth of $75\%$ . calculate the total power in the modulated wave .
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
A broad cast AM transmitter radiates $50 \;kw$ of carrier power . What will be the radiated power at $85 \%$ modulation ?
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Oct 3, 2016
by
meena.p
1
answer
A T.V tower has a height of 100 m , How much population is covered by the T.V broad cast if the average population density around the town is $5000 \;km^{-2}$?
cbse
class12
physics
ch15
sec-a
additional
medium
asked
Oct 3, 2016
by
meena.p
1
answer
Out of the following which is not an essential element of a communication system ?
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Sep 30, 2016
by
meena.p
1
answer
A repeater is a combination of
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Sep 30, 2016
by
meena.p
1
answer
If $\lambda$ is wave length of radio signals to be transmitted , then the length of Hertz antenna is
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 30, 2016
by
meena.p
1
answer
Line of sight propagation is
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Sep 30, 2016
by
meena.p
1
answer
The correct radiation between plasma frequency $\nu$ of a radio wave length and electron density N of the ionosphere
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 30, 2016
by
meena.p
1
answer
Sky wave propagation is also called
cbse
class12
physics
ch15
sec-a
additional
easy
asked
Sep 30, 2016
by
meena.p
1
answer
What is the value of frequency at which an e.m wave must be propagated for the D- region to have a refractive index of $0.49 $ Electron density for D- layer is $10^9m^{-3}$
cbse
class12
physics
ch15
sec-a
exemplar
difficult
asked
Sep 30, 2016
by
meena.p
1
answer
A T.V transmission town antenna is at a height of 20 m . How much service area can it cover if the receiving antenna at a height of 25 m
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 30, 2016
by
meena.p
1
answer
A T.V transmission town antenna is at a height of 20 m . How much service area can it cover if the receiving antenna at ground level
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 30, 2016
by
meena.p
1
answer
Compute the LC product of a tuned amplifier circuit which requires a carrier wave of $1\;MHz$ for amplitude modulation
cbse
class12
physics
ch15
sec-a
exemplar
medium
asked
Sep 30, 2016
by
meena.p
1
answer
The maximum amplitude of an A.M wave is found to be $3\;v$ What is modulation index?
cbse
class12
physics
ch15
sec-a
exemplar
medium
asked
Sep 30, 2016
by
meena.p
1
answer
Two waves A and B frequencies $2\;MHz$ and $3MHz$ respectively are beamed in the same direction for communication via sky wave .Which one of there is likely to travel longer distance in the ionosphere before suffering total internal reflection ?
cbse
class12
physics
ch15
sec-a
exemplar
medium
asked
Sep 30, 2016
by
meena.p
2
answers
Would sky waves be suitable for transmission of TV signal of $60\; MHZ$ frequency ?
cbse
class12
physics
ch15
sec-a
exemplar
medium
asked
Sep 30, 2016
by
meena.p
1
answer
Which of the following :- Would produce digital signals
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 30, 2016
by
meena.p
1
answer
Which of the following :- Would produce analog signals
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 30, 2016
by
meena.p
1
answer
A TV transmission tower has a height of $240 \;m$ signal broad cast from this will be received by LOS Communication at a distance of (assume the radius of earth to be $6.4 \times 10^6 \;m)$
cbse
class12
physics
ch15
sec-a
exemplar
medium
asked
Sep 30, 2016
by
meena.p
1
answer
An audio signal of $15\;KHz$ , frequency can not be transmitted over long distances without modulation because
cbse
class12
physics
ch15
sec-a
exemplar
medium
asked
Sep 30, 2016
by
meena.p
1
answer
Identify the mathematical expression for amplitude modulated wave
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 30, 2016
by
meena.p
1
answer
A basic communication system consists of A)transmitter B) Information Source C) User of information D) Channel E) receiver Choose the correct sequence in which these are arranged in a basic communication system
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 29, 2016
by
meena.p
1
answer
A made voice after modulation - transmission sounds like that of a female to the receiver . The problem is due to
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 29, 2016
by
meena.p
1
answer
A message signal of frequency $w_m$ is super posed on a carrier wave of frequency $w_c$ to get an amplitude modulated wave (Am). The frequency of the AM wave will be
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 29, 2016
by
meena.p
1
answer
A speech signal of $3\;kHz$ is used to modulate a carrier signal of frequency $1\;MHz$ , using amplitude modulation . The frequencies of the side band will be
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 29, 2016
by
meena.p
1
answer
A 1 Kw signal is transmitted using as communication channel which provides attention at the rate of $-2 dB$ per km. If the communication channel has a total length of 5 km , the power of the signal received is [ gain in $dB = 10 log \bigg( \Large\frac{P_0}{P_c}\bigg) ]$
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 29, 2016
by
meena.p
1
answer
A $100\;m$ antenna is mounted on a $500\;m$ tall building . The complex can become transmission tower for waves with $\lambda$
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 29, 2016
by
meena.p
1
answer
Three waves A,B and C of frequencies $1600\;kHz, 5 MHz$ and $60\;MHz$ respectively are to be transmitted from one place to another . Which of the following is the most appropriate mode of communication ?
cbse
class12
physics
ch15
sec-a
exemplar
easy
asked
Sep 29, 2016
by
meena.p
1
answer
For an amplitude modulated wave , the maximum amplitude is found to be 10 v while the minimum amplitude is found to be $2v$.What would be the value of $\mu $ if the minimum amplitude is zero volt ?
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 29, 2016
by
meena.p
1
answer
For an amplitude modulated wave , the maximum amplitude is found to be 10 v while the minimum amplitude is found to be $2v$. Determine the modulation index $\mu$ .
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 29, 2016
by
meena.p
1
answer
A modulatiy signal is a square wave as shown in the figure . The carrier wave is given . $c(t) = 2 \sin (8 \pi t) volt.$ Find modulation index.
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 29, 2016
by
meena.p
1
answer
A carrier wave of Peak voltage $12\;v$ is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of $75\%$
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 28, 2016
by
meena.p
1
answer
Is it necessary for a transmitting antenna to be at the same height on that of the receiving antenna for the line of sight communication ? A T.v transmitting antenna is $81 m$ tall.How much service area it can cover if the receiving antenna is at the ground level ?
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 28, 2016
by
meena.p
1
answer
Digital signals (i) do not provide a continuous set of values (ii) represent values as discrete steps (iii) can utilize only binary system and (iv) can utilize decimal as well as binary system . which of the following options is true ?
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 28, 2016
by
meena.p
1
answer
Frequencies in the UHF range normally propagate by means of
cbse
class12
physics
ch15
sec-a
ncert
easy
asked
Sep 28, 2016
by
meena.p
1
answer
A coil has an inductance of $5\;H$ and resistance $20\; \Omega$ . An emf of $100\; v$ is applied to it. What is the energy stored in the magnetic field, when the current has reached its final value .
cbse
class12
physics
ch7
sec-a
additional
medium
asked
Sep 28, 2016
by
meena.p
1
answer
What is the peak value of $220\;v\;a.c$
cbse
class12
physics
ch7
sec-a
additional
easy
asked
Sep 28, 2016
by
meena.p
1
answer
In a series LCR circuit , the voltage across an inductor, a capacitor and a resistor are $30\;v, 30\;v$ and $60\;v$ respectively . What is the phase difference between the applied voltage and the current in the circuit .
cbse
class12
physics
ch7
sec-a
additional
medium
asked
Sep 28, 2016
by
meena.p
1
answer
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