Class 12th

Assuming the ideal diode, draw the output waveform for the circuit given in figure, explain the waveform.

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Explanation- When the input voltage is equal to or less than 5 V, diode will be revers biased. It will offer high resistance in comparison to resistance ( ) R in series. Now, diode appears in open circuit. The input waveform is then passed to the output terminals. The result with sin wave input is to dip off all positive going portion above 5 V.

If input voltage is more than + 5 V, diode will be conducting as if forward biased offering low resistance in comparison to R. But there will be no voltage in output beyond 5 V as the

voltagebeyond+5Vwillappearacross R.

When

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7 months ago

Draw the output signals C₁ and C₂ in the given combination of gates.

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This is a Long Answer Type Questions as classified in NCERT Exemplar

A B	C D	E F	G	H	I	C₁
0 0	0 0	1 1	1	0	0	1
1 0	1 0	0 1	0	1	1	0
0 1	0 1	1 0	0	1	1	0
1 1	1 1	0 0	0	1	1	0

A B	C D	E F	G	C2
0 0	0 0	1 1	1	0
1 0	1 0	0 1	1	0
0 1	0 1	1 0	1	0
1 1	1 1	0 0	0	1

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7 months ago

In the circuit shown in figure, when the input voltage of the base resistance is 10 V, V_BEis zero and V_CE is also zero. Find the values of I_B, I_C and β .

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This is a Long Answer Type Questions as classified in NCERT Exemplar

Explanation- voltage across R_B= 10V

Resistance R_B= 400kohm

V_BE= 0, V_CE= 0, R_c=3kohm

I_B= voltage /R_B= 10/400 $*$ 10³= 25 $*$ 10^-6A

Voltage across R_c= 10V

I_c=voltage/R_c= 10/3 $*$ 10³= 3.33 $*$ 10^-3

$β = \frac{I_{c}}{I_{B}} = \frac{3.33 * 10^{- 3}}{25 * 10^{- 6}} = 133$

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7 months ago

If each diode in figure has a forward bias resistance of 25 Ω and infinite resistance in reverse bias, what will be the values of the currents I₁, I₂, I₃and I₄?

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This is a Long Answer Type Questions as classified in NCERT Exemplar

forward biased resistance = 25ohm

Reverse biased resistance = infinity

As CD branch is reverse biased having infinite resistance.

So I₃= 0

Resistance in branch AB= 25+125= 150 ohm (R₁)

Resistance in branch EF= 25+125= 150 ohm (R₂)

They both are in parallel

So $\frac{1}{R} = \frac{1}{R_{1}} + \frac{1}{R_{2}} = \frac{1}{150} + \frac{1}{150} = \frac{2}{150}$

R= 75ohm

So total resistance = 25+75= 100ohm

Current = V/R= 5/100=0.05A

I₁=I₂+I₃+I₄

I₁=I₄+I₂

Here the resistance R₁ and R₂ is same

I₄=I₂

I₁= 2I₂

I₂= I₁/2=0.05/2=0.025A

I₄= 0.025A

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7 months ago

Which of the following would produce analog signals and which would produce digital signals?
(a) A vibrating tuning fork
(b) Musical sound due to a vibrating sitar string
(c) Light pulse
(d) Output of NAND gate

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This is a Multiple Choice Questions as classified in NCERT Exemplar

Analog and digital signals are used to transmit information, usually through electric signals. In both these technologies, the information such as any audio or video is

transformed into electric signals.

The difference between analog and digital technologies is that in analog technology, information is translated into electric pulses of varying amplitude. In digital technology, translation of information is into binary formal (zero or one) where each bit is representative of two distinct amplitudes.

Thus, (a) and (b) would produce analog signal and (c) and (d) would produc

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7 months ago

In amplitude modulation, the modulation index m is kept less than or equal to 1 because
(a) m> 1, will result in interference between carrier frequency and message frequency, resulting into distortion.
(b) m > 1, will result in overlapping of both side bands resulting into loss of information
(c) m > 1, will result in change in phase between carrier signal and message signal.
(d) m > 1, indicates amplitude of message signal greater than amplitude of carrier signal resulting into distortion.

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Answer- b, d

Explanation- modulation index m= A_m/A_c

If m>1 then A_m>A_c

maximum modulation frequency m_f= frequency deviation / maximum frequency of modulating wave

here if m>1 then it means overlapping of both sides resulting loss of information.

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7 months ago

The frequency response curve (figure) for the filter circuit used for production of AM wave should be

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This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- a, b, c

Explanation- production of modulated wave is given by frequency of upper side band – frequency of lower side band so in first three cases it is clearly visible.

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7 months ago

A TV transmission 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 x 10⁶m)
(a) 100 km (b) 24 km (c) 55 km (d) 50 km

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Answer-b, c, d

Explanation- height of tower= 240m

For line of sight communication maximum distance would be d= $\sqrt[]{2 R h}$

So d= $\sqrt[]{2 * 6.4 * 10^{6} * 240}$ = 55.4km

So distance under this are communicable

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7 months ago

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 6 kHz

(c) The bandwidth required for amplitude modulation is 3 MHz

(d) The side band frequencies are 1503 kHz and 1497 kHz

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This is a Multiple Choice Questions as classified in NCERT Exemplar

Answer- b, d

Explanation- w_m=3KHz

And w_c= 1.5MHz= 1500KHz

By using these two 1500 $?$ 3= 1503 and 1497

Bandwidth = 2w_m= 2 $* 3$ = 6KHz

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7 months ago

An audio signal of 15 kHz frequency cannot be transmitted over long distances without modulation, because
(a) The size of the required antenna would be at least 5 km which is not convenient
(b) The audio signal cannot be transmitted through sky waves
(c) The size of the required antenna would be at least 20 km, which is not convenient
(d) Effective power transmitted would be very low, if the size of the antenna is less than 5 km

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