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Recent questions tagged ncert
Questions
A P-n junction is fabricated from a semiconductor with band gap of $2.8\;ev$ can it detected a wavelength of $600\;nm$?
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
Two amplifiers are connected one after the other in series (cascaded). The first amplifier has a voltage gain of $10$ and the second has a voltage gain of 20. If the input signal is $0.01\;V$ calculate the output a.c signal
cbse
class12
physics
ch-14
sec-a
ncert
medium
asked
Dec 30, 2016
by
meena.p
1
answer
A horizontal straight wire $10 \;cm$ long expending from east to west is falling with a speed of $5.0\; m/s $ at right angles to the horizontal component of the earth's magnetic field $0.30 \times 10^{-4}\;wb/m^2$. Which end of the wire is at the higher electrical potential ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 30, 2016
by
priyanka.c
1
answer
A horizontal straight wire $10 \;cm$ long expending from east to west is falling with a speed of $5.0\; m/s $ at right angles to the horizontal component of the earth's magnetic field $0.30 \times 10^{-4}\;wb/m^2$. What is the direction of the induced $emf$.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 30, 2016
by
priyanka.c
1
answer
For a common emitter amplifier , the audio signal voltage across the collector resistance of $2\;HK \Omega$ is $2V$. Suppose the current amplification factor of a transistor is 100, find the input signal voltage and base current , if the base resistance is $1\;k \;\Omega$
cbse
class12
physics
ch-14
sec-b
ncert
medium
asked
Dec 30, 2016
by
meena.p
1
answer
What is the output frequency of a full wave rectifier if the input frequency is $50\;Hz$
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
In half wave rectifier , what is the output frequency if the input frequency is $50\;Hz$?
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
For tramister amplifier , the voltage gain ,
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
For a transistor action, which of the following statements are correct ?
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
When a forward bias is applied to p-n junction , it
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
Current in a circuit falls from $5.0 A$ to $0.0 A$ in $0.1 S$. If an average $emf$ of $ 200 V$ induced, given an estimate of the self-inductance of the circuit.
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 30, 2016
by
priyanka.c
1
answer
In an unbiased p-n junction , holes different from the p-region to n-region because
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
Carbon, silicon, and germanium have four valence electrons each. These are characterized by valence and conduction bands. Seperated by energy band gap respectively equal to $(Eg)_e,(Eg)_{si}$ and $(Eg)_{Ge}$. Which of the following statement is true ?
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
A horizontal straight wire $10 \;cm$ long expending from east to west is falling with a speed of $5.0\; m/s $ at right angles to the horizontal component of the earth's magnetic field $0.30 \times 10^{-4}\;wb/m^2$. What is the instantaneous value of the $emf$ induced in the wire ?
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 30, 2016
by
priyanka.c
1
answer
A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, where does the power come from ?
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
medium
asked
Dec 30, 2016
by
priyanka.c
1
answer
Which of the statement in p-type silicon , which of the following statement is true?
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
In n-type silicon , which of the following statement is true?
cbse
class12
physics
ch-14
sec-a
ncert
easy
asked
Dec 30, 2016
by
meena.p
1
answer
A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, calculate the average power loss due to Joule heating.
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
medium
asked
Dec 30, 2016
by
priyanka.c
1
answer
A circular coil of radius $0.8\;cm$ and $20 \;turns$ is rotated about its vertical diameter with an angular speed of $50\; rad/s$ in a uniform horizontal magnetic field of magnetic $3.0 \times 10^-{2} T.$ Obtain the maximum and average $emf$ induced in the coil. If the coil forms a closed -loop of resistance $10 \Omega$, calculate the maximum value of current in the coil.
cbsc
class12
physics
electromagnetic-induction
sec-c
ncert
difficult
asked
Dec 29, 2016
by
priyanka.c
1
answer
A $1.0m $ long metallic rod is rotated with an angular frequency of $400 rad/s$ about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of $0.5 \;T$ parallel to the axis exists everywhere. Calculate the $emf$ developed between the centre and the ring.
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 29, 2016
by
priyanka.c
1
answer
A rectangular wire loop of slides $8 \;cm$ and $2\;cm$ with a small cut is moving out of a region of uniform field of magnitude $0.3T$ directed normal to the loop. What is the $emf$ developed across the cut if the velocity of the loop is $1\;cm/s$ in a direction normal to the shorter side of the loop. For how long does induced voltage last in each case.
cbsc
class-12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 29, 2016
by
priyanka.c
1
answer
A long solenoid with $15\; turns\; per\; cm $ has a small loop of area $2.0cm^2$ placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from $2.0 A \; to \;4.0 A $ in $0.1 S ,$ what is the induced $emf$ in the loop while the current is changing?
cbsc
class12
physics
electromagnetic-induction
sec-b
ncert
medium
asked
Dec 29, 2016
by
priyanka.c
1
answer
Use Lenz's law to determine the direction of induced current in the situation described by figure.
A circular loop being deformed in a narrow straight wire.
cbsc
class 12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
by
priyanka.c
1
answer
Use Lenz's law to determine the direction of induced current in the situations described by figure
A wire of irregular shape turning into a circular shape.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
by
priyanka.c
1
answer
Current (I) decreasing at a steady state.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
by
priyanka.c
1
answer
Predict the direction of induced current in situation described above.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
by
priyanka.c
1
answer
Rheostat setting being changed.
cbsc
class12
physics
electromagnetic-induction
sec-a
ncert
easy
asked
Dec 29, 2016
by
priyanka.c
1
answer
Predict the direction of induced current in the situation described above
cbsc
class12
physics
electromagnetic induction
sec-a
ncert
easy
asked
Dec 29, 2016
by
priyanka.c
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
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 small town with a demand of $800\;kw$ of electric power at $220\;v$ is situated $15\;km$ away from an electric plant generating power at $440\;v$. The resistance of the two line wires carrying power is $0.5\;\Omega$ per km. The town gets power from the lines through a $40,000-220\;v$ Step down transformation. Neglect leaked losses . hence explain why high voltage transmission is preferred .
cbse
class12
physics
ch7
sec-b
ncert
easy
asked
Sep 21, 2016
by
meena.p
1
answer
A small town with a demand of $800\;kw$ of electric power at $220\;v$ is situated $15\;km$ away from an electric plant generating power at $440\;v$. The resistance of the two line wires carrying power is $0.5\;\Omega$ per km. The town gets power from the lines through a $4000-220\;v$ Step down transformation at a substation in the town .Characterize the step up transformer at the plant
cbse
class12
physics
ch7
sec-b
ncert
easy
asked
Sep 21, 2016
by
meena.p
1
answer
A small town with a demand of $800\;kw$ of electric power at $220\;v$ is situated $15\;km$ away from an electric plant generating power at $440\;v$. The resistance of the two line wires carrying power is $0.5\;\Omega$ per km. The town gets power from the lines through a $4000-220\;v$ Step down transformation at a substation in the town . How much power must the plant supply , assuming there is negligible power loss due to leakage ?
cbse
class12
physics
ch7
sec-b
ncert
easy
asked
Sep 21, 2016
by
meena.p
1
answer
A small town with a demand of $800\;kw$ of electric power at $220\;v$ is situated $15\;km$ away from an electric plant generating power at $440\;v$. The resistance of the two line wires carrying power is $0.5\;\Omega$ per km. The town gets power from the lines through a $4000-220\;v$ Step down transformation at a substation in the town . Estimate the power loss in the form of heat
cbse
class12
physics
ch7
sec-b
ncert
easy
asked
Sep 21, 2016
by
meena.p
1
answer
At a hydroelectric power plant , the water pressure head is at a height of 300 m and the water flow available is $100 m^3 s^{-1} $. If the turbine generator efficiency is $60\%$ estimate the electric power available from the plant $(g= 9.8 ms^{-2})$
cbse
class12
physics
ch7
sec-b
ncert
medium
asked
Sep 20, 2016
by
meena.p
1
answer
A power transmission line feeds input power at $2300\;v$ to a step down transformer , with its primary winding's having $4000$ turns. What should be the number of turns in the secondary windings in order to get out put power at $230\;v$
cbse
class12
physics
ch7
sec-a
ncert
easy
asked
Sep 20, 2016
by
meena.p
1
answer
Why is choke coil needed in the use of flourscent takes with a.c mains? Why can we not use an ordinary resistor instead of choke coil ?
cbse
class12
physics
ch7
sec-a
ncert
medium
asked
Sep 20, 2016
by
meena.p
1
answer
A check coil in series with a lamp is connected to a d.c line. The lamp is seen to shine brightly and insertion of an iron core in the choke causes no change in the lamps brightness. Predict the corresponding observation if the connection is to as a.c line
cbse
class12
physics
ch7
sec-a
ncert
medium
asked
Sep 20, 2016
by
meena.p
1
answer
An applied voltage signal consists of a super position of a d.c voltage and a.c voltage of high frequency . The circuit consists of an inductor and a capacitor in series. will the d.c signal will appear across c and the a.c signal will appear across L ? At high frequencies
cbse
class12
physics
ch7
sec-b
ncert
medium
asked
Sep 20, 2016
by
meena.p
1
answer
A capacitor is used in the primary circuit of an induction coil . Why ?
cbse
class12
physics
ch7
sec-a
ncert
easy
asked
Sep 20, 2016
by
meena.p
1
answer
In any a.c circuit is the applied instantaneous voltages equal to the algebraic sum of the instantaneous voltages across the series element of the circuit ? Is the same true for r.m.s voltage?
cbse
class12
physics
ch7
sec-a
ncert
easy
asked
Sep 20, 2016
by
meena.p
1
answer
Obtain the resonant frequency and Q- factor of a series circuit with $L= 3.0 \;H,C= 27\mu F$ and $R= 7.4 \Omega$ . It is desired to improve the sharpness of resonance of the circuit by reducing its full width at half max. by a factor of 2. suggest a suitable way
cbse
class12
physics
ch7
sec-b
ncert
medium
asked
Sep 20, 2016
by
meena.p
1
answer
A series LCR circuit with $L= 0.12 H,C= 480\;nF,R= 23 \Omega $ is connected to a $230\;v$ variable frequency supply .For What frequencies of the circuit half the power at resonant frequency . What is the Q factor of the given circuit ?
cbse
class12
physics
ch7
sec-b
ncert
medium
asked
Sep 19, 2016
by
meena.p
1
answer
A series LCR circuit with $L= 0.12 H,C= 480\;nF,R= 23 \Omega $ is connected to a $230\;v$ variable frequency supply .For What frequencies of the circuit half the power at resonant frequency . What is the current amplitute at these frequencies?
cbse
class12
physics
ch7
sec-b
ncert
medium
asked
Sep 19, 2016
by
meena.p
1
answer
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