CBSE Guess > Papers > Important Questions > Class XII > 2013 > Physics > Physics - by Mr. Raghu Sharma

CBSE CLASS XII

Physics

106. The de-Broglie wave lengths, associated with a proton and a neutron, are found to be equal. Which of the two has a higher value for kinetic energy?
107. Why does a metallic plate become very hot when it is surrounded by a coil carrying high frequency alternating current?
108. Name the characteristics of electromagnetic waves that
     1. increases
     2. remains constant.
109. Four nuclei of an element fuse together to form a heavier nucleus. If the process is accompanied by release of energy, which of the two – the parent or the daughter nucleus would have a higher binding energy/nucleon?
110. Two large parallel thin metallic plates are placed close to each other. The plates have surface charge densities of opposite signs and of magnitude 20 x 10^-12 C/m². Calculate the elctric field intensity
     1. in the outer region of the plates and
     2. in the interior region between the plates.
111. The following table gives the values of work function for a few photosensitive metals. If each of these metals is exposed to radiation of wave length 300 nm, which of them will not emit photo electrons? Why?



S. No	Metal	Work Function (ev)
1	Na	1.92
2	K	2.15
3	Mo	4.17



112. The value of ground state energy of hydrogen atom is -13.6 eV.What does the negative sign signify?
113. Calculate De-broglie wavelength of an electron beam accelerated through a potential difference of 60 volt.
114. An electric lamp, connected in series with a capacitor and a.c source, is glowing with certain brightness. How does the brightness of lamp change on reducing the capacitance?
115. Sketch a graph to show how the capacitance C of a capacitor varies with the charge Q given to it.
116. What is the significance of the negative energy of electron in the orbit?
117. A parallel beam of light reflects from concave mirror. Show the reflected wave front.
118. If the colour bands on a resistor are in the order of red, yellow, orange and silver. What is the resistance of the resistor?
119. A carrier wave of peak voltage 20 V is used to transmit the message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of 80%?
120. Inputs A and B applied to the logic gates set up as shown below .Write the truth table and the name of gate formed by this set up.

121. Use Ampere’s circuital law to derive the formula for the magnetic field due to an infinitely long straight current carring wire.
122. A copper rod of length L rotates with an angular speed ω in a uniform magnetic field B. Find the induced emf developed across the two ends of a rod. The field is perpendicular to the motion of a rod.
123. Draw a labelled circuit diagram for a simple amplitude demodulator.
124. Obtain the B.E. of an α –particle in MeV.Given
125. Mass of proton = 1.007825 a.m.u, Mass of neutron = 1.00865 a.m.u, Mass of He nucleus = 4.002800 a.m.u, 1a.m.u=931MeV.
126. What is the frequency of radio waves?
127. Define SI unit of Electric flux.A photon and an electron both have same energy E. What is the Ratio of their wavelength?
128. What orientation of an electric dipole in a uniform electric field corresponds to its stable equilibrium?
129. If distance between two charges is doubled and their individual charges are also doubled. What would happen to the forces, between them.
130. The potential difference across a conductor of uniform cross-section is doubled. What happen to the drift velocity of electrons inside the conductor? 

Submitted By : Mr. Raghu Sharma
Email: [email protected]