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# Current Electricity ## 2004 - 12. How does the resistance of a good conductor vary with temperature? - 13. Two wires A and B are of same material having lengths l and 2l and diameters d and 2d respectively. If the resistance of B is 50 ohm, calculate resistance of A. - 14. Name a material whose...

# Current Electricity ## 2004 - 12. How does the resistance of a good conductor vary with temperature? - 13. Two wires A and B are of same material having lengths l and 2l and diameters d and 2d respectively. If the resistance of B is 50 ohm, calculate resistance of A. - 14. Name a material whose temperature coefficient of electrical resistance is nearly zero. - 15. In a balanced wheatstone's bridge the positions of galvanometer and battery are interchanged. Does it remain still balanced? ## 2005 - 16. Calculate the main current I in this circuit of the figure. ## 2006 - 17. State and explain kirchhoff's laws of electric circuits. Apply the laws to obtain the conditions of balance in wheatstone's bridge. ## 2007 - 18. When a wheatstone's bridge is called balanced? - 19. What is the terminal potential difference of a cell when short - circuited? - 20. When does a pure semi-conductor behave as an insulator ? - 21. Five cells each of internal resistance 0.2Ω and emf 2V are connected in series with a resistance of 4Ω. Find the current through the external resistance. ## 2008 - 22. A simple chemical cell has an emf of 2V. When the circuit containing this cell is open. What is the potential difference between the two terminals? Neglect the internal resistance of the cell? - 23. Two resistors of resistances R1 and R2 in series are connected to a source of emf E. Obtain expressions for potential difference across R1 and R2. ## 2009 - 24. Driff velocity of electrons in a conductor is of the order of - (i) a few millimetres per second - (ii) a few metres per second - (iii) a few kilometres per second - (iv) 3 x 1010 cms-1