Recent questions tagged class12

The resistance of a bulb filament is $ 100\Omega$ at a temperature of $100^{\circ}C$. If its temperature coefficient of resistance be $0.005 \: per^{\circ}C$ its resistance will become $200\Omega$ at a temperature of

asked Feb 15, 2014 by thanvigandhi_1

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In a Wheatstone's bridge their resistances P, Q and R connected in the three arms and the fourth arm is formed by the two resistances $S_1\: and \: S_2$ connected in parallel. The condition for bridge to be balanced will be

asked Feb 15, 2014 by thanvigandhi_1

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Which of the following units denote the dimensions of $\large\frac{ML^2}{Q^2}$ , where $Q$ denotes electric charge

asked Feb 15, 2014 by thanvigandhi_1

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The Kirchhoff’s first law $ (\sum i = 0)$ and second law $(\sum iR = \sum E)$ where symbols have their usual meanings, are respectively based on conservation of

asked Feb 15, 2014 by thanvigandhi_1

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A material B has twice the specific resistance of A. A circular wire made of B has twice the diameter of a wire made of A. Then for the two wires to have the same resistance, the ratio $ \large\frac{l_A}{l_b}$ of their respective lengths must be

asked Feb 15, 2014 by thanvigandhi_1

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The resistance of hot tungsten filament is about 10 times the cold resistance. What will be the resistance of 100W and 200V lamp when not in use?

asked Feb 15, 2014 by thanvigandhi_1

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In a potentiometer experiment the balancing with a cell is at length 240 cm. On shunting the cell with a resistance of $ 2 \Omega$ the balancing length becomes 120 cm. The internal resistance of the cell is

asked Feb 15, 2014 by thanvigandhi_1

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An energy source will supply a constant current into the loads of its internal resistance is

asked Feb 15, 2014 by thanvigandhi_1

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A coil of inductance 300 mH and resistance $2\Omega$ is connected to a source of voltage 2V. The current reaches half of its steady state value in

asked Feb 15, 2014 by thanvigandhi_1

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A parallel plate capacitor is made by stacking $n$ equally spaced plates connected alternatively. If the capacitance between any two adjacent plates is C then the resultant capacitance is

asked Feb 15, 2014 by thanvigandhi_1

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A heater coil is cut into two equal parts and only one part is now used in the heater. The heat generated will now be

asked Feb 15, 2014 by thanvigandhi_1

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Two sources of equal emf are connected to an external resistance R. The internal resistance of the two sources are $R_1\: and \: R_2 (R_2 > R_1)$. If the potential difference across the source having internal resistance $R_2$ is zero then,

asked Feb 15, 2014 by thanvigandhi_1

1 answer

In the circuit the galvanometer $G$ shows zero deflection. If the batteries A and B have negligible internal resistance, the value of the resistor $R$ will be

asked Feb 15, 2014 by thanvigandhi_1

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Two voltameters one of copper and other of silver, are joined in parallel. When a total charge $q$ flows through a voltameters, equal amount of metals are deposited. If the electrochemical equivalents of copper and silver are $z_1\: and \: z_2$ respectively the charge which flows through the silver voltameter is

asked Feb 15, 2014 by thanvigandhi_1

1 answer

A moving coil galvanometer has 150 equal divisions. Its current sensitivity is 10 divisions per milliampere and voltage sensitivity is 2 divisions per millivolt. In order that each division reads 1 volt, the resistance in ohms needed to be connected in series with the coil will be

asked Feb 15, 2014 by thanvigandhi_1

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Let $ \varepsilon_0$ denote the dimensional formula of the permittivity of vacuum. If M = mass, L = length and T = time and A = electric current then,

asked Feb 15, 2014 by thanvigandhi_1

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In an LCR circuit as shown below both switches are open initially . Now switch $S_1$ is closed $S_2$ kept open. ( q is charge on the capacitor and $\tau = RC$ is capacitive time constant ) which of the following statement is correct ?

asked Feb 15, 2014 by thanvigandhi_1

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What is the dimensional formula for inductance?

asked Feb 15, 2014 by thanvigandhi_1

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What is the dimensional formula for capacitance?

asked Feb 15, 2014 by thanvigandhi_1

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What is the dimensional formula for resistivity?

asked Feb 15, 2014 by thanvigandhi_1

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A 5V battery with internal resistance $2\Omega$ and a 2V battery with internal resistance $1\Omega$ are connected to a $ 10 \Omega $ resistor as shown in the figure. The current in the $ 10\Omega $ resistor is

asked Feb 15, 2014 by thanvigandhi_1

1 answer

6 boys and 6 girls sit randomly in a row, what is thae probability that boys and girls sit alternately?

asked Feb 14, 2014 by bharathdon.999

1 answer

An equi - convex lens of crown and equi convex lens of flint glass make an achromatic system. The radium of curvature of convex lens is $0.54\;m$. If the focal length of combination for mean colour is 1.5 m and $RI$ for crown glass are $\mu _R= 1.53$ and $\mu_v =1.55$ Then the dispersive power of flint glass is

asked Feb 14, 2014 by meena.p

1 answer

integrate 1/1+x3

asked Feb 14, 2014 by sriku270_1

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Consider a block of conducting material of resistivity $ \rho$ shown in the figure. Current I enters at A and leaves from D. We apply superposition principle to find voltage $ \Delta V$ developed between B and C. The calculation is done in the following steps. \[\] (i) Take current I entering from A and assume it to spread over a hemispherical surface in the block. \[\] Calculate field E(r) at distance r from A by using ohm's law $E= \rho j$, where j is the current per unit area at r. \[\] (iii) From the r dependence of E(r) obtain the potential V(r) at r. \[\] (iv) Repeat (i), (ii) and (iii) for current I leaving D and superpose results for A and D \[\] For current entering at A, the electric field at a distance r from A is

asked Feb 14, 2014 by thanvigandhi_1

1 answer

Consider a block of conducting material of resistivity $ \rho$ shown in the figure. Current I enters at A and leaves from D. Apply the superposition principle and find the voltage $ \Delta V$ developed between B and C?

asked Feb 14, 2014 by thanvigandhi_1

1 answer

In a YDSE $\lambda =60 \;nm\; D= 2m\;\lambda=6 mm$. Find the positions of a point lying b/w third maxima and third minima where the intensity in three - fourth of maximum intensity on the screen .

asked Feb 14, 2014 by meena.p

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When the screen is moved away from plane of slits in YDSE then the effect on interference fringes is

asked Feb 14, 2014 by meena.p

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How much $CaCO_3$ is present in 100ml of 1000ppm $CaCO_3$ solution?

asked Feb 14, 2014 by sreemathi.v

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1000 mL of aqueous solutions of $CaCO_3$ contains 1 gm of carbonate,concentration of the solution is

asked Feb 14, 2014 by sreemathi.v

1 answer

At 293K temperature,the Henry's Law constants for $He,H_2,N_2$ and $O_2$ are 144 kbar,69 kbar,76 kbr and 34.86 kbar respectively. Which of the following show maximum solubility in water at a given pressure

asked Feb 14, 2014 by sreemathi.v

1 answer

In an interference arrangement similar to YDSE , Slits $S_1\;and \;S_2$ are illuminated with coherent microwave sources and are synchronized to have zero phase difference The slits are separates by distance $d= 150 \;m$. The intensity $I_0$ is measured as a function of $\theta$ where $\theta$ is defined as shown. If $I _0$ is max intensity, calculate $I_0$ for $\theta=90^{\circ}$

asked Feb 14, 2014 by meena.p

1 answer

A parallel plate capacitor with air between the plates has a capacitance of $9\: pF$. The separation between the plates is $d$ . The space between the plates is now filled with two dielectrics. One of the dielectrics has dielectric constant $k_1=3$ and thickness $ \large\frac{d}{3}$ while the other has dielectric constant $k_2=6$ and thickness $ \large\frac{2d}{3}$. Capacitance of the capacitor is now

asked Feb 14, 2014 by thanvigandhi_1

1 answer

For the following disproportion reaction $3Br_2+6OH^{-}\rightarrow 5Br^-+BrO_3^-+3H_2O$. Correct statement below is (Given $Br_2$ molecular mass is 160)

asked Feb 14, 2014 by sreemathi.v

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Shown in the figure below is a meter-bridge setup with null deflection in the galvanometer.The value of the unknown resistor $R$ is

asked Feb 14, 2014 by thanvigandhi_1

1 answer

Which of the following statements about Raoult's Law is/are correct?

asked Feb 14, 2014 by sreemathi.v

1 answer

A thin plano- convex lens of focal length f is split into two halves one of halves is shifted along the optical axis. The separation b/w object and image plane is 1.8 m. The magnification of image formed by one of half lenses is 2. Find the focal length of lens and separation b/w the two halves.

asked Feb 14, 2014 by meena.p

1 answer

$PtCl_4.6H_2O$ can exist as a hydrated complex. If 1 molal aqueos solution has a depression in freezing point of $3.72^{\large\circ}$,assuming 100% ionization and $K_f$ of $1.86^{\large\circ}mol^{-1}kg$ which of the following is the complex in question?

asked Feb 14, 2014 by sreemathi.v

1 answer

Calculate the effective resistance between points A and B

asked Feb 14, 2014 by thanvigandhi_1

1 answer

Relative decrease in vapour pressure of an aqueous glucose dilute solution is found to be 0.018.What is the elevation in boiling point? (Given 1 molal aq.glucose solution boils at 100.62$^{\large\circ}C$ at 1 atm.pressure)

asked Feb 14, 2014 by sreemathi.v

1 answer

What is the average drift speed of conduction electrons in a copper wire of cross-sectional area $1.0 \times 10^{–7}m^2$ carrying a current of $1.5 A$. Assume that each copper atom contributes roughly one conduction electron. The density of copper is $ 9.0 \times 10^3 kg/m^3 $ , and its atomic mass is $ 63.5 u.$

asked Feb 14, 2014 by thanvigandhi_1

1 answer

The cross section of glass prism has the form of an isosceles triangle . One of equal face is silvered. A ray of light incident normally on other equal face and after being reflected twice, emerges through base of prism along normal. That the angle of prism is :-

asked Feb 14, 2014 by meena.p

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At what temperature would the temperature of a copper conductor be double its value at $0^{\circ}C\: \alpha_{Cu} = 4 \times 10^{-3}$

asked Feb 14, 2014 by thanvigandhi_1

1 answer

12.2gm of benzonic acid (M=122) in 100gm benzene has depression in freezing point $2.6^{\large\circ}C$; $K_f = 5.2 ^{\circ} mol^{-1}kg$. If there is 100% polymerization, the number of molecules of benzonic acid in associated state is

asked Feb 14, 2014 by sreemathi.v

1 answer

Which of the following is an example of ohmic conductor:

asked Feb 14, 2014 by thanvigandhi_1

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The van't Hoff factor of $CH_3COOH$ is less than unity. It indicates that the acetic acid

asked Feb 14, 2014 by sreemathi.v

1 answer

The 2.56gm of sulphur in 100gm of $CS_2$ has depression in freezing point of $0.010^{\large\circ}$C. $K_f=0.1^{\large\circ}C$/molal. Hence atomicity of sulphur in $CS_2$

asked Feb 14, 2014 by sreemathi.v

1 answer

Which of the following has the maximum osmotic at temperature T?

asked Feb 14, 2014 by sreemathi.v

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Two identical charged spheres are suspended by strings of equal length . The strings make an angle of $\;60^{0}\;$ with each other . When suspended in a liquid of density $\;0.5 g/cc,\;$ the angle remains the same . The dielectric constant of the liquid is [density of material of sphere is $\;1.5 g/cc\;$]

asked Feb 14, 2014 by yamini.v

2 answers

A lens has a power of +5 diopter in air what will be its power if completely immersed in water ? $ \mu_g =\large\frac{3}{2};$$ \mu_w=\large\frac{4}{3}$

asked Feb 14, 2014 by meena.p

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