Mr. Ramcharan Jain, a 68 years old man, complained of neck pain. One day his grandson Kabir suggested that magnetic therapy is very effective in reducing such pain. Mr. Ramcharan contacted with concern medical clinic. After that, he get that therapy and felt better. |
(i) What values did Kabir exhibit towards his grandfather? |
(ii) Where is the magnetic field due to a current element be minimum? |
A large circular coil of radius R and a small circular coil radius r are put in vicinity of each other. If the coefficient of mutual induction for this pair, equals 1 mH, what would be the flux linked with the larger coil when a current of 0.5 A flows through the smaller coil? |
When the current in the smaller coil falls to zero, what would be its effect in the larger coil? |
Or |
Show that the total induced charge simply depends upon the change in the magnetic flux and is independent of the time rate of change of flux. |
How will its capacitance be affected, if |
(i) the foil is electrically insulated? |
(ii) the foil is connected to the upper plate with a conducting wire? |
A light of wavelength 630 nm incident on a pair of slits produces an interference pattern in which two successive bright fringes are separated by 7.2 mm. |
Calculate the wavelength of another source of light which will produce interference fringes separated by 8.1 mm using same pair of slits. |
Shivam is a student of class 12th. He asked his father Mr. Brijesh, "which waves produce greenhouse effect?" Mr. Brijesh replied that question and also explained the negative impact of this effect on our environment. |
(i) What values did Mr. Brijesh exhibit towards his son? |
(ii) Name that waves which produces greenhouse effect and its uses. |
Lata usually enjoyed loud music. One day her music system was not working. She get disappointed. She shared this issue with her brother Mahendra. He advised her to connect an amplifier in series with amplifier of stereosystem. |
After doing that, Lata got happy. |
(i) Which value is displayed by Mahendra? |
(ii) Why the loudness of music system gets increased on connecting with amplifier? Write down current gain in the transistor as an amplifier. |
A long straight wire of a circular cross-section of radius a, carries a steady current I. The current is uniformly distributed across the cross-section of the wire. Use Ampere's circuital law to show that the magnetic field, due to this wire, in the region inside the wire, increases in direct proportional to the distance of the field point from the axis of the wire. |
Write the value of this magnetic field on the surface of the wire. |
(i) What is meant by half-life of a radioactive element? |
(ii) The half-life of a radioactive substance is 50 s. Calculate |
(a) the decay constant and |
(b) time taken for the sample to decay by \[\frac{3}{4}th\] of the initial value. |
(i) Use the mirror equation to show that a convex mirror always produces a virtual image independent of the location of the object. An object placed between the pole and focus of a concave mirror produces a virtual and enlarged image. |
(ii) Use the lens equation deduce algebraically that an object placed with in the focus of a convex lens produces a virtual and enlarged image. |
A circular coil of 200 turns and radius 10 cm is placed in a uniform magnetic field of 0.5 T, parallel to the plane of the coil. If the current in the coil is 3 A, calculate the |
(i) total torque on the coil. |
(ii) total force on the coil. |
(iii) average force on each electron in the coil, due to the magnetic field. |
Assume the area of cross-section of the wire to be \[{{10}^{-5}}{{m}^{2}}\] and the free electron density is \[{{10}^{29}}{{m}^{-3}}.\] |
Look at the circuit given below. Six resistors, each of value \[4\,\Omega \] are joined together. Calculate equivalent resistance across the points A and B. If a cell of emf 2 V is connected across AB, compute the current through the arms AB and DF of the circuit. |
Circuit diagram |
(i) Sketch the amplitude modulated waveform. |
(ii) What is the modulation index? |
In a college's classroom, the fan above the professor was not working properly. Due to this, the professor was sweating and restless. All the students wanted to resolve the problem. They called for an electrician, who came and changed the capacitor only after that the fan started working properly. |
(i) What values did the students have? |
(ii) What energy is stored in the capacitor? |
(iii) On what factors, does the capacitance of a capacitor depend? |
How can you improve the quality factor of a parallel resonance circuit. Obtain the resonant frequency and quality factor of a series L-C-R circuit with L = 4 H, \[C=64\mu F\] and \[R=20\,\Omega .\] |
Or |
A resistor of \[200\,\Omega .\] and a capacitor of \[40\,\mu \,F\] are connected in series to 220 V AC source with angular frequency \[(\omega )=300\] Hz. Calculate the voltage (rms) across the resistor and the capacitor. Why is the algebraic sum of these voltages more than the source voltage? How do you resolve this paradox? |
Rekha and Priya are classmates. Priya is a bright student and has a quick grasping power. |
However, Rekha noticed that, Priya was not good in study, from the past few days, Rekha found out that, Priya was not able to see the letters on the board properly and also complained of frequent headaches. Rekha suggested to Priya to get her eye checkup. Priya followed her suggestion. She felt very comfortable after wearing the prescribed spectacles. |
(i) What kind of girl is Rekha? |
(ii) What was the eye defect that Priya had? |
(iii) How can it be corrected? |
(i) Using the necessary circuit diagram, draw the transfer characteristics of a base-biased transistor in CE configuration. With the help of these characteristics, explain briefly how the transistor can be used as an amplifier. |
(ii) Why are NAND gate called universal gates? Identify the logic operations carried out by the circuit shown below |
Logic circuit |
Or |
(i) Draw a circuit diagram to study the input and output characteristics of an n-p-n transistor in its common emitter configuration. Draw the typical input and output characteristics. |
(ii) Explain, with the help of a circuit diagram, the working of n-p-n transistor as a common emitter amplifier. |
(ii) An air capacitor has a capacitance of \[2\,\mu F,\] which becomes \[12\,\mu \,F\] when a dielectric medium is filled in the space between the plates. Find (a) dielectric constant of that material, (b) induced charge on the dielectric due to polarisation of a charge of \[6\,\mu \,C\] is given to the positive plate of the capacitor. |
Or |
A non-conducting disc of radius 'r' and uniform positive surface charge density \[\sigma \] is placed on the ground, with its axis along Z-axis. A particle of mass m and positive charge q is dropped, along the axis of the disc, from a height H with zero initial velocity. The particle has \[q/m=4{{\varepsilon }_{0}}g/\sigma .\] |
(i) Find the value of H if the particle just reaches the disc. |
(ii) Draw the graph of its potential energy as a function of its height and find its equilibrium position from the centre of the disc. |
Unpolarised light of intensity \[32\text{ }W{{m}^{-2}}\] passes through three polarisers such that the transmission axis of last polariser is crossed with the first. If the intensity of the emerging light is \[3\,W{{m}^{-2}},\] then |
(i) What is the angle between the transmission axes of the first two polarisers? |
(ii) At what angle will the transmitted intensity be maximum? |
Or |
(i) In what way is diffraction from each slit related to the interference pattern in a double slit experiment? |
(ii) Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily? |
(iii) When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen. Suggest a possible explanation. |
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