## Chapter No.11 : Heat (Watch)

11.1 (i) The Normal human body temperature is 98.6 degree F.What is this temperature of Celsius scale?(ii) At what temperature do the Celsius and Fahrenheit scale coincide? 11.2 A steel rod has length of exactly 0.2 cm at 30 degree Celsius .What will be its length at 60 degree Celsius? 11.3 Find the change in the aluminum sphere of 0.4 m radius when it is heat from 0 to 100 degree Celsius? 11.4 Calculate the root mean square speed of hydrogen molecule at 800 K . 11.5 (a) Determine the average value of kinetic energy of the particles of an ideal gas at 0 degree Celsius and 50 degree Celsius. (b) What is the kinetic energy per mole of an ideal gas at these temperatures? 11.6 A 2 kg iron block is taken from a furnace where its temperature was 650 degree C and placed on a large block of ice at 0 C. Assuming that all heat given by iron is used to melt the ice, how much ice is melted? 11.7 In a certain process 400 J of heat is supplied to a system and at the same time 150 J of work is done by the system .What is the increase in internal energy of the system? 11.8 There is an increase in internal energy of 400 J when 800 J of work is done by the system .What is the amount of heat supplied during this process? 11.9 A heat engine performs 200 j of work in each cycle and has efficiency of 20 % for each cycle of operation (a) how much heat is absorbed and (b) how much heat is expelled? 11.10 A heat engine operated between two reservoirs of temperature of 25 C and 300 C.What is the maximum efficiency of this engine? 11.11 The low temperature reservoir of a carnot engine is at & degree Celsius and has a efficiency of 40%.How much the temperature of high temperature reservoir be increased to increase the efficiency to 50%?

## Chapter No.12 : Electrostatics

12.1 Two unequal point charges repel each other with a force of 0.2 N when they are 10 cm apart.Find the force which each exerts on other when they are 1 cm apart. 12.2 Two point charges 1 x 10 -4 C and -1 x 10 -4 C are placed at a distance of 40 cm from each other. A charge of 6 x 10 5 C is placed midway between them .What is the magnitude and direction of force on it? 12.3 Three point charges each of 4 micro Care placed at three corners of the square of side 20 cm.Find the magnitude of force on each? 12.4 Three charges q1- 7 x 10 -6 ,q2=-4 x 10 -6 and q3=-5 x 10-6 are placed at the vertices of triangle as shown in the diagram. The sides of the triangle measure 3,4 and 5 cm Determine the direction and magnitude of force on charge q1. 12.5 Two small spheres each of mass 0.1 gm ,are suspended from the same point by silk threads each of 20 cm long .The spheres are given equal charges and they are found to repel each other coming to rest 24 cm apart. Find the charge on each.

12.6 Two charges of +2 x 10 -7 C and -5 x 10 -7 C are placed at a distance of 50 cm from each other.Find a point on the line joining the charges at which the electric field is zero. 12.7 What are the electric field and potential at the center of a square whose diagonals are 60 cm each , when (a) charges each of 2 micro C are placed at four corners and (b) charges of 2 micro C are placed on the adjacent corners and -4 micro C on the other corners? 12.8 A particle carrying a charge of 10 -5 C starts from rest in a uniform intensity of 50 V/m.Find the force on the particle and kinetic energy it acquires when it has moved 1 m. 12.9 Proton of mass 1.67 x 10 -27 kg and charge 1.6 x 10-19 C is to be held motionless between two horizontal plates 10 cm apart.Find the voltage required to be applied between plates. 12.10 A small sphere of weight 5 x 10 -3 N is suspended by a silk thread 50 mm long which is attached to a point on a large charged insulating plane.When a charge of 6 x 10 -8 C is placed on the ball, the thread makes an angle of 30 degrees.What is the charge density on the plane? 12.11 How many electrons should be removed from each of the two similar spheres each of 10 gm so that electrostatic repulsion be balanced by gravitational force?