## Saturday, 9 June 2018

### ASSIGNMENT 2 CLASS XII

Q11) The sequence of bands marked on a carbon resistor are: Red, Red, Red, Silver. Write the value of resistance with tolerance.
Q12) A wire of resistivity ρ is stretched to three times its initial length, what will be its new resistivity.
Q13) state the working principle of potentiometer explain with the help of circuit diagram how the emf of two primary cells are compared by using the potentiometer
Q14) State Kirchhoff’s law an electrical network. Using the Kirchhoff’s laws deduce the condition for balance in the Wheat-stone bridge.
Q15) A Voltmeter, an ammeter and a resistance are connected in series with a battery. There is
some deflection in voltmeter but the deflection of ammeter is zero. Explain why?
Q16)Draw a neat and labelled diagram of a cyclotron . State the underlying the principle and explain how a positively charged particle will get accelerated. Show mathematically the cyclotron frequency does not depend upon speed of the particle
Q17) With the help of a labelled diagram the underlying  principle and working of a moving coil galvanometer. What is the function of
ii) soft iron core in such a device.
Q18) . Three resistance 3Ω,6Ω and 9Ω are connected to a battery. In which of them will the power dissipation be maximum if
a) They all are  connected in parallel
b) They all are connected in series     Give reason
Q19) Prove that current density of a metallic conductor is directly-proportional to the speed of electrons.
Q20) . Draw a graph showing variation of resistivity with temperature for
a) nichrome
b)silicon
Q21) Two long straight wires are set parallel to each other. Each carries a current I in the same
direction and the separation between them is 2r.Find the force produced. Identify its nature( mention the rule to identify)

### ASSIGNMENT 1 CLASS XII

Q1) What is an electric polarization of a dielectric? What is the effect on capacitance of a capacitor when a dielectric of width ‘t’ is placed between the two plates of parallel plate capacitor?

Q2) What is electric potential? Give its SI unit. Find the expression for the electric potential at any point due to a point charge.
Q3) State gauss’s theorem. Use it to find electric field due infinite line of charge. What is the effect on electric field, when charge density gets double and distance between point and line of charge is half.
Q4) The electric field in a region is radially outward and varies with distance r as E=250 r Vm-1Calculate the charge contained in a sphere of radius 0.2 m centered at the origin
Q5) A 4µF capacitor is charged by a 200V supply. The supply is then disconnected and the charged capacitor is connected to another uncharged 2µF capacitor. How much electrostatic energy of the first capacitor is lost in the process of attaining the steady situation?
Q6)A parallel plate capacitor with air between the plates has a capacitance of 8 pF . The separation between the plates is now reduced by half and the space between them is filled with a medium of dielectric constant 5. Calculate the value of capacitance of parallel plate capacitor in second case.
Q7) Charge of 2C is placed at the centre of a cube of volume 8 cm3. What is the electric flux passing through one face?
Q8)What orientation of an electric dipole in a uniform electric field corresponds to stable equilibrium?
Q9) Name the physical quantity whose SI unit is JC-1.Is it a scalar or a vector quantity?
Q10) What is the amount of work done in moving 100 µC charge between two points 5 cm apart
on an equipotential surface?

### ASSIGNMENT 2

RAY OPTICS CLASS XI
 Q12)Where  should an object be placed from a converging lens of focal length 20cm so as to obtain a real image of magnification 2? Q13)Write the difference between dispersive and non dispersive medium with examples. Q14)Show that lateral displacement is directly proportional to t and i1. Q15)What is the main requirement in the fabrication of optical fibres?  How it can be achieved? Write two examples Q16)Obtain a relation for refraction from a rarer to denser medium at a convex spherical surface forming real image. Q17)Derive thin lens formula for a concave lens . Q18)A double convex lens made of glass of refractive index 1.5 has both curvatures of radii 20cm. An object 2cm high is placed 2cm from this lens , find the position, nature and size of the image. Q19)The angle of minimum deviation for yellow light in a prism of refractive index 1.6 is found to be 460. Calculate refracting angle of the prism. Q20)Derive lens makers formula. Q21)For refraction through prism derive prism formula.