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CBSE - Class 12 Physics Communication Systems Worksheet

Select the correctly punctuated sentence;

Spain is beautiful country; the beache's are warm, sandy and spotlessly clean.

Spain is beautiful country: the beaches are warm, sandy and spotlessly clean.

Spain is beautiful country, the beaches are warm, sandy and spotlessly clean.

Spain is beautiful country; the beaches are warm, sandy and spotlessly clean.

(i) Draw the plot of amplitude versus ‘$\omega$’ for an amplitude modulated wave whose carrier wave ($\omega_c$) is carrying two modulating signals, $\omega_1$ and $\omega_2$ ($\omega_2 > \omega_1$).

You take ________ many chances when you drive from that cliff.

too

two

Many myths say that vampires are stronger, quicker, and more agile when the air is cold and the full moon is unobscured by clouds.

NO CHANGE

quick, and more

quicker, and they are

quicker, being more

Why are you so late? I've been standing here _______ 7:30.

For

Since

Student to teacher: _________ ! what shall I do now?

I am finishing

I finished

I've finished

I am finish

To ________, Anne was on time for math class.

Everybody's surprise

Every body's surprise

Everybodys surprise

On radiating (sending out) an AM modulated signal, the total radiated power is due to energy carried by $\omega_c$, $\omega_c - \omega_m$ & $\omega_c + \omega_m$. Suggest ways to minimise cost of radiation without compromising on information.

Audio sine waves of 3 kHz frequency are used to amplitude modulate a carrier signal of 1.5 MHz. Which of the following statements are true?

a. The side band frequencies are 1506 kHz and 1494 kHz. b. The bandwidth required for amplitude modulation is 6kHz. c. The bandwidth required for amplitude modulation is 3 MHz. d. The side band frequencies are 1503 kHz and 1497 kHz.

10.

(ii) Is the plot symmetrical about $\omega_c$? Comment especially about plot in region $\omega < \omega_c$.

11.

Randolph ________ my invitation to dinner.

accepted

expected

12.

My school is still searching for ways to hire high-quality teachers, lower the cost of tuition, and keep a balanced budget.

NO CHANGE

and keeping a balanced budget

and to keep a balanced budget

and for ways to keep a balanced budget

13.

All of the people at the school, including the teachers and ________ were glad when summer break came.

Students:

Students,

Students;

Students

14.

Which of the following sentences is punctuated correctly.

Is that your mother’s car? - No it’s my sisters.

Is that your mothers’ car? - No it’s my sisters.

Is that your mother’s car? - No it’s my sister’s.

Is that your mothers car? - No it’s my sisters’.

15.

2. WHO SHOOK THE DUST OF SNOW ON THE POET ROBERT FROST ?

SPARROW

CRANE

GOLDFINCH

CROW

16.

(iii) Extrapolate and predict the problems one can expect if more waves are to be modulated.

17.

It's ok. I've only been waiting ________ a few minutes.

For

Since

18.

A TV trasmission tower has a height of 240 m. Signals broadcast from this tower will be received by LOS communication at a distance of (assume the radius of earth to be $6.4 \times 10^6$ m)

a. 100 km. b. 24 km. c. 55 km. d. 50 km.

19.

For each of the following, choose the sentences in which the subject and verb agree.

Sandals and towels are essential gear for a trip to the beach.

Sandals and towels is essential gear for a trip to the beach.

20.

The maximum frequency for reflection of sky waves from a certain layer of the ionosphere is found to be $f_{\text{max}} = 9\sqrt{N_{\text{max}}}$, where $N_{\text{max}}$ is the maximum electron density at that layer of the ionosphere. On a certain day it is observed that signals of frequencies higher than 5MHz are not received by reflection from the $F_1$ layer of the ionosphere while signals of frequencies higher than 8MHz are not received by reflection from the $F_2$ layer of the inonosphere. Estimate the maximum electron densities of the $F_1$ and $F_2$ layers on that day.

Worksheet Answers

Option D

Option B

Option A

Option B

Option C

Option A

11.

Option A

12.

Option B

13.

Option B

14.

Option C

15.

Option D

17.

Option A

18.

19.

Option A

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