18 12 The velocity of charge carriers of current about 1 ampere in a metal under normal conditions is of the order of a a fraction of mm sec b velocity of light c several thousand metres second d a few hundred metres per second 3 6 Limitations of Ohm s Law 13 The resistance of a discharge tube is a non ohmic b ohmic c zero Current 14 From the graph between current I and voltage V is shown Identify the portion corresponding to negative resistance d both b and c 1999 BC E A Voltage a CD b DE c AB d BC a 470 k2 5 c 4 7 k2 5 1991 3 7 Resistivity of Various Materials 15 The color code of a resistance is given below 1997 Yellow Violet Brown Gold The values of resistance and tolerance respectively are b 47 k2 10 d 470 92 5 NEET 2020 16 A carbon resistor of 47 4 7 kQ2 is to be marked with rings of different colours for its identification The colour code sequence will be a Violet Yellow Orange Silver b Yellow Violet Orange Silver c Yellow Green Violet Gold d Green Orange Violet Gold NEET 2018 17 Identify the set in which all the three materials are good conductors of electricity a Cu Hg and NaCl b Cu Ge and Hg c Cu Ag and Au d Cu Si and diamond WtGNEET AIPMT Chapterwise Topicwise Solutions Physic 3 8 Temperature Dependence of Resistivity 18 Which of the following graph represents the variation of resistivity p with temperature T for copper a c P P NEET 202 19 The solids which have the negative temperatu coefficient of resistance are a metals c semiconductors only d insulators and semiconductors b NEET 202 20 Specific resistance of a conductor increases with a increase in temperature b increase in cross section area d c increase in cross section and decrease in lengt d decrease in cross section area 200 21 Copper and silicon is cooled from 300 K to 60 K t specific resistance a fuse c inductor a b insulators only a decreases in copper but increases in silicon b increases in copper but decreases in silicon c increases in both d decreases in both c 3 9 Electrical Energy Power 22 Which of the following acts as a circuit protectie device a R 2b a R 6b 23 NEET 201 The charge flowing through a resistance R vari with time t as Q at bt where a and b are positi constants The total heat produced in R is a R b b b conductor d switch 200 d a R 3b NEET I 201 1994 24 Two cities are 150 km apart Electric power is se from one city to another city through copper wire The fall of potential per km is 8 volt and the avera resistance per km is 0 5 92 The power loss in the wire is a 19 2 W b 19 2 kW c 19 21 d 12 2 kW 201