Sita and her brother Ramesh were travelling on bike. Sita was sitting behind her brother. At a place traffic signal turned red from green and Ramesh continued riding. Sita noticed red Signal and stopped her brother Ramesh. Her brother felt happy on Sita's intelligence. |
(i) What kind of value is expressed by Sita? |
(ii) What are the principles that are used in maintaining traffic signals? |
A parallel plate capacitor with air between the plates has a capacitance of 8 pF. The separation between the plates is now reduced by its half and the space between them is filled with a medium of dielectric constant 5. Calculate the value of the capacitance of the capacitor in the second case. |
Or |
Two metal plates form a parallel plate capacitor. The distance between the plates is d. A metal sheet of thickness d/2 and of the same area is introduced between the plates. What is the ratio of the capacitances in the two cases? |
Name the constituent radiation of electromagnetic spectrum which |
(i) is used for studying crystal structure. |
(ii) is absorbed from sun light by ozone layer. |
(iii) produces intense heating effect. |
(iv) is used in cellular phones to transmit voice communication. |
(v) is used for sterilising surgical instruments. |
(vi) is used for taking photograph in foggy season. |
Some students of \[XI{{I}^{th}}\] class went to visit a science exhibition. They saw the process of electroplating. The students exhibited to see electroplating with the help of DC source. Immediately students raised the doubt, the teacher incharge explained and cleared their doubts. |
(i) What values were displayed by the students? |
(ii) Why should we use DC instead of AC? |
A radioactive sample contains 2.2 mg of pure \[_{6}^{11}C\] which has half-life of 1224 seconds. |
Calculate |
(i) the number of atoms present initially |
(ii) the activity when \[5\mu g\] of the sample will be left. |
A group boys went to Kavalur in Tamilnadu, an observatory, housing the largest telescope in India. The instructor Mr. Jay Verma explained the different types of telescope, the diameter of the objective (2.75m) and other details. The boys were looking forward to see through the telescope. |
(i) What type of telescope is explained by Mr. Jay? |
(ii) Mention two advantages of this telescope. |
(iii) What kind of person is Mr. Jay? |
(i) What is the ratio of the number of holes and the number of conduction electrons in an intrinsic semiconductor? |
(ii) How does the energy gap in an intrinsic semiconductor vary when doped with a pentavalent impurity? |
(iii) Draw / versus V graph of a forward biased junction diode. |
(i) resistance R is increased, keeping all parameters unchanged. |
(ii) resistance S is increased, keeping R constant. |
(iii) cell P is replaced by another cell whose emf is lower than that of cell Q. |
Calculate |
(i) the impedance of the circuit and |
(ii) the peak value of the current flowing in the circuit |
(iii) the power factor of this circuit and compare this value with the one at its resonant frequency. |
Using Bohr's postulates for hydrogen atom, show that the total energy (E) of the electron in the stationary states can |
be expressed as the sum of kinetic energy (K) and potential energy (U). Show that, \[K=-U/2.\] |
A bar magnet M is dropped so that it falls vertically through the coil C. Obtain the graph for voltage produced across the coil versus time. |
(i) Explain which quantity is depicted by the area of graph. |
(ii) Why is the negative peak longer than the positive peak? |
Define the term work function of a metal. The threshold frequency of a metal is \[{{f}_{0}}.\] When the light of frequency \[2{{f}_{0}}\] is incident on the metal plate, the maximum velocity of electrons emitted is \[{{K}_{1}}.\] When the frequency of the incident radiation is increased to \[5{{f}_{0}},\] the maximum velocity of electrons emitted is \[{{k}_{2}}.\] Find the ratio of \[{{V}_{1}}\] to \[{{V}_{2}}.\] |
Or |
The following graph shows the variation of stopping potential \[{{V}_{s}}\]with the frequency (v) of the incident radiation for two photo sensitive metals X and Y. |
(i) Which of the metals has larger threshold wavelength? Give reasons. |
(ii) Explain giving reason which metal gives out electrons having larger kinetic energy for the same wavelength of incident radiation. |
(iii) If the distance between the light source and metal X is halved, then what will be the kinetic energy of electron emitted due to this change? Give reasons. |
A slit of width 'a' is illuminated by light of wavelength 700 nm, what will be the value of slit width 'a' when |
(i) First minimum falls at an angle of diffraction \[30{}^\circ ?\] |
(ii) First maximum falls at an angle of diffraction \[30{}^\circ ?\] |
(iii) Find the angular spread of central maximum if the slit width a = 4.0 cm. (Assume incidence normal to the plane of the slip) |
Amar and Kishan were going to their friend's house by walking. It was a hot sunny day of summer. Amar faced difficulty to see around him. While Kishan had cooling sunglasses. Kishan did not face such problem as Amar faced. Kishan explained the features of sunglasses to Amar and also advised him to buy them. |
(i) What values are shown by Kishan? |
(ii) Name the phenomenon on which cooling sunglasses works. |
(iii) What is the resulting intensity of light, if both polariser and analyser are rotated through same angle? |
Two best friends John and Jolly are students of \[XI{{I}^{th}}\] class, John wants to be an astronaut but he does not know anything about astronomy. So, he shared his desire with his friend Jolly. Jolly asked him to take advice from his teacher. |
(i) In which chapter John would be keen to learn astronomy and what should he do? |
(ii) Draw ray diagram of terrestrial telescope. |
(iii) Calculate the separation between two points on the moon that can be resolved using 550 cm telescope. The distance between the moon and the earth is \[3.8\times {{10}^{8}}m.\] The wavelength most sensitive to human eye is \[5500\,\overset{{}^\circ }{\mathop{A}}\,.\] |
What does the term LOS communication mean? Name the type of waves that are used for this communication. Give typical example with the help of suitable figure of communication systems that use space wave mode propagation. |
Or |
(i) Describe briefly the three factors which justify the need for translating a low frequency signal into high frequencies before transmission. |
(ii) Figure shows a block diagram of a detector for AM signal. |
Draw the waveforms for the |
(a) input AM wave at A. |
(b) output B at the rectifier. |
(c) output signal at C. |
(i) Draw a labelled diagram of a moving coil galvanometer and explain its working. What is the function of radial magnetic field inside the coil? |
(ii) How is moving coil galvanometer converted into a voltmeter? Explain, giving the necessary circuit diagram and the required mathematical relation used. |
Or |
(i) Find an expression for the force acting on a current carrying straight conductor kept in a uniform magnetic field. State the rule used to determine the direction of this force. |
(ii) What is the magnitude of magnetic force per unit length on a wire carrying current of 8 A and making an angle \[30{}^\circ \] with the direction of uniform magnetic field of 0.5 T. |
(i) A 2m insulating slab with a large aluminium sheet of area \[/{{m}^{2}}\] on its top is fixed by a man outside his house one evening. Will he get an electric shock, if he touches the metal sheet next morning? |
(ii) Two identical capacitors of plate dimensions \[1\times b\] and plate separation d have dielectric slabs filled in between the space of the plates as shown in the figures. |
Calulate |
(i) the electric flux through the cube |
(ii) the charge within the cube |
Where the side of cube = 0.1 m |
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