State the energy changes in the following cases while in use:
(a) loudspeaker (b) a steam engine
(c ) microphone (d) washing machine
(e) a glowing electric bulb (f) burning coal
(g) a solar cell (h) bio-gas burner
(i) an electric cell in a circuit (j) a petrol engine of a running car (k) an electric iron (l) a ceiling fan
(m) an electromagnet

Classify the following into elements, compounds and mixtures. (a) Sodium (b) Soil (c ) Sugar solution (d) Silver (e ) Calcium carbonate (f) Tin (g) Silicon (h) Coal (i) Air (j) Soap (k) Methane (l) Carbon dioxide (m) Blood

Which separation techniques will you apply for the separation of the following ? (a) Sodium chloride from its solution in water. (b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride. (c ) Small pieces of metal in the engine oil of a car. (d) Different pigments from an extract of flower petals. (e ) Butter from curd. (f) Oil from tea. (g) Tea leaves from tea. (h) Iron pins from sand. (i) Wheat grains from husk. (j) Fine mud particles suspended in water.

(a) what is the rate at which energy being delivered to a light bulb higher : just after it is turned on , the glow of the filament is increasing , or after it has been on for a few seconds and the glow is steady ? (b) IF a piece of wire is used to connect points b and c in Fig. 7.9, does the brightness of bulb R_(1) increase , decrease or stay constant ? What happens to the brightness of bulb R_(2) ? (I_(1) = I_(2) = I) (c) Compare the brightness of four identical light bulbs in Fig. 7.10 . What happens if the bulb A fails so that it cannot conduct ? What if C fails ? What if D fails? (d) If electric power is transmitted over long distances, the resistance of the wires becomes significant. Why ? Which mode of transmission would result in less energy losss: high current and low voltage or low current and high voltage ? Discuss. (e) In Fig. 7.11 , describe wha happens to the light bulb after the switch is closed . Assume the capacitor has a large capacitance and is initially uncharged. (f) Astuident claims that a second light bulb in series is less bright than the first , because the first bulb uses up some of the current . How would you respond to this statement ? (g) If you were to design an electeric heater using nichrome wire as the heating element , what parameters of the wire would you vary to meet a specific power output , sch as 1000 W ?

In given circuit determine (a) Equivalent resistance (Including internal resistance). (b) Current I, i_(1), i_(2)'" and "i_(3) ( c) Potential difference across battery and each resistance (d) The rate at which the chemical energy of the cell is consumed (e ) The rate at which heat is generated insisde the battry (f) Electric power output (g) Which resistance consumes miximum power ? (h) Power dissipated across 4Omega resistance.

A fuel cell is a cell that is continously supplied with an oxidant and a reductant so that if can deliver a current indefinitely. Fuel cells offer the possibility of achieving high thermodynamic efficiency in the conversion of Gibbs energy into mechanical work.Internal combustion engines at best convert only the fraction (T_2-T_1)//T_2 of the heat of combustion into mechanical work. While the thermodynamic efficiency of the fuel cell is given by, eta=(DeltaG)/(DeltaH) , where DeltaG is the Gibbs energy change for the cell reaction and DeltaH is the enthalpy change of the cell reaction.A hydrogen-oxygen fuel cell may have an acidic or alkaline electrolyte. Pt|H_2(g)|H^(+)(aq.)||H_2O(l)|O_(2)(g)|Pt , (2.303 RT)/F=0.06 The above fuel cell is used to produce constant current supply under constant temperature & 30 atm constant total pressure conditions in a cylinder.If 10 moles H_2 and 5 moles of O_2 were taken initially. Rate of consumption of O_2 is 10 milli moles per minute. The half-cell reactions are 1/2O_2(g)+2H^+(aq)+2e^(-)toH_2O(l) E^(@)=1.246 V 2H^+(aq)+2e^(-) to H_2(g) E^(@)=0 To maximize the power per unit mass of an electrochemical cell, the electronic and electrolytic resistances of the cell must be minimized.Since fused salts have lower electolytic resistances than aqueous solutions, high-temperature electrochemical cells are of special interest for practical applications. Calculate e.m.f of the given cell at t=0.(log 2=0.3)

Write the chemical formula of the following compounds in a step by step manner a. Potassium choride b. sodium bromide c. Potassium nitrate d. Calcium hydroxide e. Calcium bicarbonate f. Sodium bisulphate g. Potassium sulphate h. Zinc hydroxide i. Potassium permanganate j. Potassium dichromate k. Aluminium hydroxide l. Magnesium nitride m. sodium zincate n. copper II oxide o. Copper (I) sulphide p. Iron [III] chloride q. Iron [II] hyrdoxide r] Iron [III] sulphide s. Iron [III] oxide.

A solid insulating sphere of radius a carries a net positive charge 3Q , uniformly distributed throughout its volume. Concentric with this sphere is a conducting spherical shell with inner radius b and outer radius c and having a net charge -Q, as shown in figure a. Consider a spherical Gaussian surface of radius rgtc, the net charge enclosed by this surface is ............. b. The direction of the electric field rgtc is ............. c. The electric field at rgtc is ............... . d. The electric field in the region with radius r, which cgtrgtb, is ............... e. Consider a spherical Gaussian surface of radius r, where cgtrgtb , the net charge enclosed by this surface is ................ . f. Consider a spherical Gaussian surface of radius r, where bgtrgta , the net charge enclosed by this surface is ................. . g. The electric field in the region bgtrgta is ................ . h. Consider a spherical Gaussian surface of radius rlta . Find an expression for the net charge Q(r) enclosed by this surface as a function of r. Note that the charge inside the surface is less than 3Q. i. The electric field in the region rlta is ................. . j. The charge on the inner surface of the conducting shell is .......... . k. The charge on the outer surface of the conducting shell is .............. . l. Make a plot of the magnitude of the electric field versus r.

State the following statements as TRUE or FALSE. a. A convex mirror cannot from a real image for a real object. b. The image formed by a convex mirror is always diminished and erect. c. Virtual image formed by a concave mirror is always enlarged. d. Only in the case of a concave mirror, it may happen that the object and its image move in same direction. e. In the case of a concave mirror, the image always move faster than the object. f. If an object is placed in front of a diverging mirror at a distance equal to its focal length, then the height of image formed is half of the height of object. g. For two positions of an object , a concave mirror can form englarged image. h. Concave mirror is used as a rear view mirror in motor vehicles. i. If some portion of the mirror ois covered, then complete image will be formed but of reduced brightness. j. A plane mirror always forms an erect iamge of same size as that of the object. k. The image formed by a plane mirror has left-right reversal. l. A virtual object means a converging beam.

Fuel cells : Fuel cells are galvanic cells in which the chemical energy of fuel cell is directly converted into electrical energy. A type of fuel cell is a hydrogen - oxygen fuel cell. It consists of two electrodes made up of two porous graphite impregnated with a catalyst ( platinum, silver, or metal oxide ). The electrodes are placed in aqueous solution of NaOH . Oxygen and hydrogen are continuously fed into the cell. Hydrogen gets oxidized to H^(o+) which is neutralized by overset(c-)(O)H, i.e., anodic reaction. At cathode, O_(2) gets reduced to overset(c-)(O)H Hence, the net reaction is The overall reaction has DeltaH=-285.6 kJ mol^(-1) and DeltaG=-237.4 kJ mol^(-1) at 25^(@)C What is the value of DeltaS^(c-) for the fuel cell at 25^(@)C ? a. -1600 J K^(-1) b. -160 J K^(-1) c. 160 J K^(-1) d. 1600 J K^(-1)