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Recent questions tagged boardexam
Questions
A die which is marked with 1, 2, 3 in red and 4, 5, 6 in green is tossed. Let A be the event 'number is even' and B be the event 'number is red' and Are A and B independent?
cbse
class12
maths
ch13
sec-b
boardexam
2017
asked
Nov 17, 2016
by
priyanka.c
1
answer
(i) Find the magnitude and direction of current in $1 \Omega$ resistor in the given circuit . (ii) Two students X and Y perform an experiment on potentio meter separately using the circuit diagram shown below. Keeping other things unchanged (a) X increases the value of resistance R, (b) Y decrease the value of resistance S in the set up. How will these change affect the position of null point in each case and why ? (a) Use Kirchhoff's rules , calculate the current in the arm AC of the given circuit ? (b) On what principle does the meter bridge work ? Why are the metal strips used in the bridge ?
cbse
class12
physics
sec-e
boardexam
2016
asked
Jun 10, 2016
by
meena.p
1
answer
Draw a ray diagram showing the geometry of formation of image of a point object situated on the principal axis and on the convex side of a spherical surface of radius of curvature R. Taking the rays as incident from a rarer medium of refractive index $n_1$ to a denser medium of refractive index $n_2$ derive the relation. $\large\frac{n_@}{v} -\frac{n_1}{u} = \frac{n_2-n_1}{R}$, Where symbols have their usual meaning ? (ii) Explain briefly how the focal length of a convex lens changes with increase in wave length of incident light . (iii) What happens to the focal length of convex lens when it is immersed in water ? Refractive index of the material of lens is greater than water .
cbse
class12
physics
sec-e
boardexam
2016
asked
Jun 9, 2016
by
meena.p
1
answer
When a parallel beam of monochromatic source of light of wave length incident on a single slit of width, show how the diffraction pattern is formed at the screen by the interference of the wavelets from the slit.
cbse
class12
physics
sec-e
boardexam
2016
asked
Jun 9, 2016
by
meena.p
1
answer
(a) Consider a beam of charged particles moving with varying speeds.Show how crossed electric and magnetic fields can be used to select charged particles of a particular velocity ? (b) Name another device / machine do and what are the functions of magnetic and electric fields in this machine ? Where do these exists in this machine ? Write about their natures .
cbse
class12
physics
sec-e
boardexam
2016
asked
Jun 9, 2016
by
meena.p
1
answer
Express Biot-savart law in the vector form. (ii) Use it to obtain the expression for the magnetic field at an axial point, distance d from the center , of a circular coil of radius R carrying current I. (iii) Also , find the ratio of the magnitudes of the magnetic field of this coil at the center at an axial point for which $x= R\sqrt 3$
cbse
class12
physics
sec-e
boardexam
2016
asked
Jun 9, 2016
by
meena.p
1
answer
During a thunderstorm the 'live' wire of the transmission line fell down on the ground from the poles in the street. A group of boys, who passed through,noticed it and some of them wanted to place the wire by the side. As they were approaching the wire and trying to lift the cable, Anuj noticed it and immediately pushed them away, thus preventing them from touching the live wire. During pushing some of them got hurt. Anuj took them to a doctor to get them medical aid. Based on the above paragraph, answer the following questions : (a) Write the two values which Anuj displayed during the incident. (b) Why is it that a bird can sit on a suspended 'live' wire without any harm whereas touching it on the ground can give a fatal shock ? (c) The electric power from a power plant is set up to a very high voltage before transmitting it to distant consumers. Explain, why.
cbse
class12
physics
sec-d
boardexam
2016
asked
Jun 9, 2016
by
meena.p
1
answer
Derive an expression for the electric field intensity at a point on the equatorial line of an electric dipole moment $\overrightarrow{P}$ and length 2a. What is the direction of this field ?
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 9, 2016
by
meena.p
1
answer
(i) Name the phenomenon on which the working of an optical fiber is based ? (ii) What are the necessary condition for this phenomenon to occur ?
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 9, 2016
by
meena.p
1
answer
(i) For a glass prism $(\mu = \sqrt 3 )$ the angle of minimum deviation is equal to the angle of the prism. Calculate the angle of the prism . (ii) Draw ray diagram when incident ray falls normally on one of the two equal sides of a right angled isosceles prism having refractive index $\mu = \sqrt 3$
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 8, 2016
by
meena.p
1
answer
(a)Define the term "intensity of radiation " in photon picture. (b) . plot a graph showing the variation of photo current vs collector potential for three different intensities $I_1 > I_2 > I_3$, two of which $(I_1$ and $I_2)$ have the same frequency v and the third has frequency $v_1 > v$ (c) Explain the nature of the curves on the basis of Einstein's equation .
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 8, 2016
by
meena.p
1
answer
Draw a circuit diagram of a common emitter amplifier using n-p-n transistor . Derive an expression for the current gain $\beta _{ac}$
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 8, 2016
by
meena.p
1
answer
Plot a graph showing the variation of binding energy per nucleon as a function of mass number. Which property of nuclear force explains the approximate constancy of binding energy in the range $30 < A < 170$ ? How does one explain the release of energy in both the processes of nuclear fission from the graph ?
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 8, 2016
by
meena.p
0
answers
Plot a graph showing the variation of binding energy per nucleon as a function of mass number. Which property of nuclear force explains the approximate constancy of binding energy in the range $30 < A < 170$ ? How does one explain the release of energy in both the processes of nuclear fission from the graph ?
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 8, 2016
by
meena.p
1
answer
Derive an expression for the axial magnetic field of a finite solenoid of length 2l and radius r carrying current I. Under what condition does the field become equivalent to that produced by a bar magnet ?
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 8, 2016
by
meena.p
1
answer
(i) Mention two properties of soft iron due to which is preferred for making an electromagnet ? (ii) State Gauss's law in magnetism. How is it different from Gauss's law in electrostatics and why ?
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 8, 2016
by
meena.p
1
answer
Three identical capacitors each of capacitance $3 \mu F$ are connected in term in series and in parallel combination to the common source of V volt . find out the ratio of the energies stored in two configurations.
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 7, 2016
by
meena.p
1
answer
A parallel plate capacitor $(C_1)$ having charge Q is connected to an identical uncharged capacitor $C_2$ in series. What would be the charge accumulated on the capacitor $C_2$?
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 7, 2016
by
meena.p
1
answer
Mention any three applications of the internet. explain one of these in detail .
cbse
class12
physics
boardexam
2016
sec-e
asked
Jun 7, 2016
by
meena.p
1
answer
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