25 25 A piece of wire of resistance R is cut into three equal parts. These parts are then connected in parallel. If the equivalent resistance of this parallel combination is R, what is the value of the ratio R : R? OR Refer to the image below and state how the magnetic field pattern indicates regions where the magnetic field is stronger outside the magnet? What happens to the magnetic field when the current in the circuit is reversed? solenoid magnetic field line 26 Study the food chain given below and answer the questions that follow: Leaf Caterpillar Chameleon Mongoose Snake a) If the amount of energy available at the third trophic level is 100 joules, then how much energy will be available at the producer level? Justify your answer. b) Is it possible to have 2 more trophic levels in this food chain just before the fourth trophic level? Justify your answer. 27 28 29 30 The given reaction shows one of the processes to extract the metals like Iron and Manganese. MnO2 (s) + Al(s) Mn(1) + Al2O3(s) + Heat a) Give reason why the above reaction is known as a thermite reaction. b) Identify the substance oxidised and reduced in the above reaction. c) Give a reason why Aluminium is preferably used in thermite reactions. An element 'M' with electronic configuration 28 3 combines separately with C1, SO4 anions. Write the chemical formulae of the compounds formed. Predict with the suitable reason the nature of the bond formed by element 'M' in general. How will the electrical conductivity of the compounds formed vary with respect to 'M'? OR A reddish-brown metal 'X', when heated in air, gives a black compound 'Y', which when heated in presence of H2 gas gives 'X' back. 'X' is refined by the process of electrolysis; this refined form of 'X' is used in electrical wiring. Identify 'X' and 'Y'. Draw a well-labeled diagram to represent the process of refining 'X'. We are advised to take iodised salt in our diet by doctors. Justify it's importance in our body. What is the probability of a girl or a boy being born in a family? Justify your answer.