Physics | ICSE Board | Grade 12 | 2012
Q. Threshold frequency of a certain metal for photo-electric emission is 5×1014Hz. Calculate its work function.
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Q. In the circuit shown in figure, E is a battery of emf 6V and internal resistance 1Ω. Find the reading of the ammeter A, if it has negligible resistance.

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Q. Figure shows five dc sources(cells). Their emfs are shown in the figure. Emf of the battery AB is.

1. 8V
2. 16V
3. 4V
4. 2
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Q. What conclusion was drawn by Rutherford based on Geiger-Marsden's experiment on scattering of alpha particles?
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Q. Figure shows a point P near a long conductor XY carrying a current 1. MN is a short current carrying conductor, kept at the point P, parallel to the conductor XY.
(i) What is the direction of magnetic flux density 'B' at the point P due to the current flowing through XY?
(ii) What is the direction of the force experienced by the conductor MN due to the current flowing through XY?

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Q. Write a balanced nuclear reaction showing emission of a β-particles by 23490Th. (symbol of daughter nucleus formed in the process is Pa.)
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Q. A point charge of 5×106C experiences a force of 2×103N when kept in a uniform electric field of intensity E. Find E.
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Q. A thin convex lens (L1) of focal length 80cm and a thin concave lens(L2) of focal length f are kept co-axially, 20cm apart as shown in figure. When a narrow and parallel beam of light is incident on the convex lens, beam emerging from the concave lens is also a parallel beam. Find f.

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Q. In a moving coil galvanometer, what is meant by a radial magnetic field?
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Q. A body has a positive charge of 8×1019C. It has :
1. an excess of 5 electrons
2. a deficiency of 5 electrons
3. an excess of 8 electrons
4. a deficiency of 8 electrons
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Q. Which electromagnetic radiation has wavelength greater than that of X rays and smaller than that of visible light?
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Q. Write an expression of magnetic flux density 'B' at a point in end-on position or an axial position of a magnetic dipole. (Derivation not required.)
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Q. State Brewster's law of polarisation of light.
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Q. State one important use of a Zener diode.
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Q. Variation of alternating current 'I' with time 't' is shown in the graph. What is the rms value of this current?

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Q. What condition must be satisfied by two thin lenses kept in contact so that they form an achromatic doublet, i.e., a combination free from chromatic aberration?
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Q. Binding energy of a nucleus is of the order of.
1. Electron volt (eV)
2. Kilo electron volt (KeV)
3. Mega electron volt (MeV)
4. A joule (J)
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Q. Three point charges Q1=25μC, Q2=50μC and Q3=100μC, are kept at the corners A, B and C respectively of an equilateral triangle ABC having each side equal to 7.5m. Calculate the total electrostatic potential energy of the system.
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Q. Obtain an expression for equivalent capacitance C, when three capacitors having capacitance C1, C2 and C3 are connected m series.
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Q. What is the essential difference between the working of a nuclear reactor and that of a fission bomb?
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Q. A 50μF capacitor, a 30Ω resistor and a 0.7H inductor are connected in series to an ac supply which generates an emf 'e' given by e=300sin (200t) Volt. Calculate peak value of the current flowing through the circuit.
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Q. Which conservation principle is involved in Kirchhoff's first law of electric circuits?
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Q. White light is passed through sodium vapours contained in a thin walled glass flask and the transmitted light is examined with the help of a spectrometer. The spectrum so obtained is.
1. Solar spectrum
2. Band spectrum
3. Continuous spectrum
4. Absorption spectrum
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Q. On the basis of Huygen's wave theory, prove Snell's law of refraction of light.
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Q. When a potential difference of 3V is applied between the two ends of a 60cm long metallic wire, current density in it is found to be 1×107Am2. Find conductivity of the material of the wire in SI system.
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Q. How did Fresnel construct a biprism in order to study interference of light?
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Q. With the help of a neatly drawn and labelled diagram, obtain balancing condition of a Wheatstone bridge.
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Q. State any two differences between Peltier effect and Joule effect.
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Q. Which one of the following graphs in following figure represents variation of reactance Xc of a capacitor with frequency 'f' of an ac supply?

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Q. What are four different types of energy losses in a transformer? State how to reducel minimize any one of them.
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