Recent questions in Model Papers

$ \sqrt { 1+ \large\frac{x}{144}}=\frac{13}{12}$ then x is equal to

asked Feb 11, 2015 by meena.p

1 answer

a)A capacitor is used in the primary circuit of induction coil why? b)A power transmission line feeds input power at $2300\;V$ to a step down transformer with its primary windings having $4000$ turns. What should be the number of turns in the secondary in order to get the output power at $230\;V$? c)What is the peak value at $22V\; AC$?

asked Feb 11, 2015 by meena.p

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Derive an expression for the impedance of a series L-C-R circuit connected to an AC supply of variable frequency. Plot a graph showing the variation of current with the frequency of the applied voltage. Explain briefly how the phenomenon of resonance in the circuit can be used in the tuning mechanism of a radio or a TV set?

asked Feb 11, 2015 by meena.p

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An AC voltage of peak $20\;V$ is connected in series with a silicon diode and a load resistance of $500 \Omega$. The forward resistance of the diode is $10 \Omega$ and the barrier voltage is $0.7\;V$. Find the peak current through diode and the peak voltage across the load. What will happen to these values if the diode is assumed to be ideal?

asked Feb 11, 2015 by meena.p

1 answer

Why is Zener diode considered as a special purpose semiconductor diode? Draw the I-V characteristics of Zener diode and explain briefly how reverse current suddenly increase at the breakdown voltage? Describe briefly with the help of a circuit diagram how a Zener works to obtain a constant DC voltage from the unregulated DC output of a rectifier?

asked Feb 11, 2015 by meena.p

0 answers

a)Define the term decay constant and half life of a radio active sample. Derive the relation connecting the two. b)How many disintegration per second will occur in one gram of $_{92}U^{238},$ if its half life against alpha decay is $1.42 \times 10^{17}\;s$?

asked Feb 11, 2015 by meena.p

0 answers

Using Bohr’s postulates, derive the expression for the frequency of radiation emitted when electron in hydrogen atom undergoes transition from higher energy state quantum number $(ni)$ to the lower state $(nf)$. When electron in hydrogen atom jumps from energy state $ni = 4$ to $nf = 3,2,1,$ identify the spectral series to which the emission lines belong.

asked Feb 11, 2015 by meena.p

0 answers

Shwetha on entering her apartment switched on the tubelight, but only found it not to work. She called on an electrician. He inspected it and suggested to change the choke. On replacing it, she found it to work properly. 1. What is the function of the choke coil? 2. Identify the value exhibited here. 3. Why is a capacitor used in the primary circuit of an induction coil?

asked Feb 11, 2015 by meena.p

0 answers

A) An infinite line charge produces a field of $9 \times 10^4 N/C$ at a distance of $2\;cm$. Calculate the linear charge density b)An arbitrary surface encloses a dipole. What is the electric flux through this surface?

asked Feb 11, 2015 by meena.p

0 answers

Give reasons, (1).For ground wave transmission, size of the antenna $(l) $ should be comparable to wavelength of signal i.e; $l = \large\frac{\lambda}{4}$ (2). Audio signals, converted into an e.. wave, are not directly transmitted as such. 3. The amplitude of modulating signal is kept less than the amplitude of carrier wave.

asked Feb 11, 2015 by meena.p

0 answers

A resistor of resistance $4000 \Omega$ and a capacitor of resistance $200 \Omega$ are connected in series to a $220\;V\; 50\; Hz$ a.c. source. If the currents in the circuit is $0.49$ ampere, find the 1. Voltage across the resistor and capacitor. 2. Value of inductance required so that voltage and current are in phase.

asked Feb 11, 2015 by meena.p

0 answers

In a metre bridge experiment a student observed a balance point at the point J, where AJ = l. Draw the equivalent Wheatstone Bridge circuit diagram for this setup The values of R and X are both doubles and then interchanged. What would be the new position of the balance point? If in this set up, the galvanometer and battery are interchanged at the balance position, how will the balance point get affected?

asked Feb 11, 2015 by meena.p

1 answer

1.Name the type of biasing of a p-n type junction diode so that the junction offers a very high resistance. 2.Name two factors on which the electrical conductivity of a pure semiconductor at a given temperature depends. 3. Identify the logic gates marked x and y in the following figure. Write down the output as when A = 1 , B = 1 and A = 0 and B = 0

asked Feb 11, 2015 by meena.p

0 answers

A) Why photoelectric effect cannot be explained on the basis of wave nature of light? Give reasons. b) Write the basic features of photon picture of electromagnetic radiation on which Einsteins’s photoelectric equation is based.

asked Feb 10, 2015 by meena.p

1 answer

In Young’s double slit experiment, the two slits $0.15\;m$ apart are illuminated by monochromatic light of wavelength 450nm.$ The screen is $1.0\;m$ away from the slits. 1. Find the distance of the second a) bright fringe b) dark fringe from the central maximum. 2. How will the fringe pattern change, if the screen is moved away from the slits?

asked Feb 10, 2015 by meena.p

1 answer

In a plane electromagnetic wave, the electric field oscillates sinusoidally at a frequency of $2.0 x 10^{10}Hz$ and amplitude $48V/m$ 1. What is the wavelength of the wave? 2. What is the amplitude of the oscillating magnetic field? 3. Show that the average energy density of the $E$ field equals the average density of the B field.

asked Feb 10, 2015 by meena.p

0 answers

A $4 \mu F$ capacitor is charged by a $200\;V$ supply. Then, it is disconnected from the supply and is connected to another uncharges $2 \mu F$ capacitor. How much electrostatic energy of the first capacitor is lost in the form of heat and electromagnetic radiation?

asked Feb 10, 2015 by meena.p

0 answers

Two charged conducting spheres of radii a and b are connected to each other by a wire. What is the raio of elecetric field at the surfaces of the two spheres? Use the result obtained to explain why charge density on the sharp and pointed ends of the conductor is higher than at its flatter portions?

asked Feb 10, 2015 by meena.p

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The angle of dip at a place in Kerala is $18^{\circ}$. Will its value be more or less at a place in Kashmir.? Give reasons?

asked Feb 10, 2015 by meena.p

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Define the term ‘angle of dip’. Derive the relation between the angle of dip and the resultant magnetic field of earth at a place .

asked Feb 10, 2015 by meena.p

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A light bulb is rated $100 w$ for $220 \;V \;AC$ supply of $50\; Hz$. Calculate. A) resistance of the bulb B) the rms current of the bulb

asked Feb 10, 2015 by meena.p

0 answers

Use Lenz’s law to determine the direction of induced current in the situations described by the figure. 1. A wire of irregular shape turning into a circular shape 2. A circular loop being deformed into a narrow straight wire.

asked Feb 10, 2015 by meena.p

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A proton has spin and magnetic moment just like an electron. Why is its effect neglected in magnetism of materials ?

asked Feb 10, 2015 by meena.p

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The output of a $NAND$ gate is fed to a $NOT$ gat. Write the truth table for the final output of the combination.

asked Feb 10, 2015 by meena.p

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Define $\alpha$ and $\beta$ of a transistor . How are they related?

asked Feb 10, 2015 by meena.p

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Two metal plates have a work function of $2eV$ and $5eV$. Which metal will emit electrons, when it is radiated with light of wavelength $400\;nm$ and why?

asked Feb 10, 2015 by meena.p

0 answers

What is meant by data retrieval?

asked Feb 10, 2015 by meena.p

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What is space communication? What are the modes of communication?

asked Feb 10, 2015 by meena.p

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Why do we prefer a potentiometer to measure the emf of a cell rather than a voltmeter?

asked Feb 10, 2015 by meena.p

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Give the logic symbol for NOR gate.

asked Feb 10, 2015 by meena.p

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An electron does not suffer any deflection while passing through a region of magnetic field. What is the direction of the magnetic field?

asked Feb 10, 2015 by meena.p

0 answers

Evaluate : $\int \large\frac{1- \cos x}{\cos x(1+\cos x)}$$dx$

asked Feb 10, 2015 by meena.p

1 answer

Evaluate : $\int \large\frac{1}{1+ 3 \sin ^2 x +8 \cos ^2 x}$$dx$

asked Feb 10, 2015 by meena.p

1 answer

An amount of $Rs. 5000$ is put into three investments at the rate of interest of $6\%,7\%$ and $8\%$ per annum respectively . The total annual income is $Rs. 385$ If the combined income from the first two investments is $Rs. 70$ more than the income from the third , find the amount of each investment by matrix method.

asked Feb 10, 2015 by meena.p

1 answer

If a machine is correctly setup, it produces $90\%$ acceptable items. If it is incorrectly setup, it produces only $40 \% $ acceptable items . past experience shows that $80\%$ of the setups are correctly done . If after a certain setup, the machine produces 2 acceptable items, find the probability that machine is correctly setup.

asked Feb 10, 2015 by meena.p

0 answers

Let the point $(2,3,4)$ lie on the top of Tajmahal. Find the perpendicular distance of the point $(2,3,4)$ from the line $\large\frac{(4x)}{2}=\frac{y}{6} =\frac{(1-z)}{3}$.Also find the coordinates of the perpendicular. Do you think that heritage is important is important for the country and its people ?

asked Feb 10, 2015 by meena.p

0 answers

If the length of the three sides of a trapezium other than the base are equal to 10 cm , then find the area of the trapezium when it is maximum .

asked Feb 10, 2015 by meena.p

1 answer

Find the area bounded by the curve $y= 2x-x^2$ and the straight line $y=-x$

asked Feb 10, 2015 by meena.p

1 answer

Compute the area bounded by the lines $x+2y =2 ; y-x =1$ and $2x+y=7$

asked Feb 10, 2015 by meena.p

1 answer

A small manufacturer has employed 5 skilled men 10 semi - skilled men and makes an article in two qualities deluxe model and an ordinary model. The making of a deluxe model requires 2 hrs work bt skilled man and 2 hrs work by a semi skilled man. The ordinary model requires 1 hr by a skilled man and 3 hrs by a semi skilled man. By union rules no mam may work more than 8 hrs per day. The manufactures clear profit on deluxe model is Rs.15 and an orsinary model is Rs. 10. How many of each type should be made in order to maximize his total daily profit.

asked Feb 10, 2015 by meena.p

1 answer

Prove that $\large\frac{dy}{dx}=\frac{[\sin ^2(a+y)]}{\sin a}$

asked Feb 10, 2015 by meena.p

0 answers

Find the distance between the planes, $2x-y+2z=-3$ and $-2y+4x+4z+5=0$

asked Feb 10, 2015 by meena.p

0 answers

Find the cartesian equation of the line passing through the points , $A(2,-1,3)$ and $B(4,2,1)$

asked Feb 10, 2015 by meena.p

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Find the cartesian equation of the line passing through the points , $A(2,-1,3)$ and $B(4,2,1)$

asked Feb 9, 2015 by meena.p

0 answers

Find a unit vector perpendicular to each of the vectors , $\overrightarrow{a}+\overrightarrow{b}$ and $\overrightarrow{a}- \overrightarrow{b}$ where $\overrightarrow{a}= 3 \hat i +2 \hat j+2 \hat k$ and $\overrightarrow{b}= \hat i +2 \hat j- 2\hat k$

asked Feb 9, 2015 by meena.p

0 answers

Find the intervals in which $f(x) = \log (1+x) \large\frac{-x}{(1+x)}$

asked Feb 9, 2015 by meena.p

1 answer

Find the points on the curve $4x^2+9y^2=14$, where the tangents are perpendicular to the line $2y +x =0$

asked Feb 9, 2015 by meena.p

1 answer

Use differentials to find the approximate value of $\sqrt {0.037}$

asked Feb 9, 2015 by meena.p

1 answer

If $x^{my^n}=(x+y)^{m+n}$, prove that $\large\frac{dy}{dx}=\frac{y}{x}$

asked Feb 9, 2015 by meena.p

1 answer

If $x^y =e^{(x-y)}$, prove that $\large\frac{dy}{dx}= \large\frac{\log x}{(1+\log x)^2}$

asked Feb 9, 2015 by meena.p

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