CBSE Guess Paper 2010

Physics

Class - XII

Q1. What is the force experienced by a positively charges particle Q moving at right angles to a uniform electric field E.

Q2. Name the electromagnetic radiations to which the following wavelengths belongs

          (a)10^-2m (b) 1A⁰

Q3. A glass rod is rubbed with a silk cloth. Explain what will happen to their mass and charge? Why does this change occur?

Q4. Name the phenomenon responsible for the reddish appearance of the sun at sunrise and sunset.

Q5. What is the angle b/w Electric field and Dipole moment at an axial point?

Q6. Name two types of commercially available resistors.

Q7. Name the S.I. Unit of (i) magnetic flux (ii) Magnetic-induction.

Q8. 2 charges are placed R mts apart in air. The repulsive force b/w them is found to be F. Find the force when the same charges are placed in water at a distance of 2R. (Є_r = 80 ). Will this force be attractive or repulsive?

Q9. Derive the value of electric field at the axial and equatorial point of a dipole made of charges +q and –q placed a distance 2a apart.

Q10. The work function for a certain metal is 4.2 ev. Will this metal give photoelectric emission for incident radiation of wavelength 330 nm?

Q11. Two resistors are connected in parallel b/w A and B to give a net resistance of 2 ohms. When one of these resistors is broken, the net resistance becomes a 3 ohms. What is the resistance of the resistor that was broken?

Q12. A system has two charges q₁=2.5x10^-7 C and q₂=-2.5x10^-7 C located at points A (0,0,-15cm) and B(0,0,+15cm) respectively what are the total charge and electric dipolemoment of the system?

Q13. Using Gauss theorem derive the value of electric field due to an infinite sheet of charge having charge density σC/m² .Draw a graph showing the variation of electric field with distance R.

Q14. Two convex lenses A and B of an astronomical telescope having focal lengths 5 cm. and 20cm. respectively, are arranged as shown in fig below:-

                             

     (i) Which one of the two lenses you will select to use as an objective lens and why?

     (ii) What should be the change in the distance between the lenses to have the telescope in its normal adjustment position?

      (iii) Calculate the magnifying power of the telescope in the normal adjustment position.

Q15. (a) Using a labeled diagram explain the construction and working of a moving coil galvanometer. Define its current and voltage sensitivity and explain how they can be increased.

(b) A galvanometer with a coil resistance of 5 ohm can tolerate a maximum current of 10mA. Explain how this can be converted into an ammeter of range 1A.