question_answer

  What   is   the   relation  between resistanced and current potential difference? Give SI unit of resistance. Draw graph for following data. Give two examples of conductors which obey Ohm's law.

I	0.2	0.4	0.6	0.8	1.0	1.2	1.4
V	0.8	1.6	2.4	3.2	4.0	4.8	5.6

Or What is electromagnet? How is it used in a scrap yard? How is strength of electromagnet increased? On what principle is electromagnet based?

Answer:

  The relation between resistance potential difference and current is V= IR                                                            (1) SI unit of resistance                                                                                                                                                (1) Copper and silver obey Ohm's law.                                                                                                                                          (1) The I-V graph is shown below On putting the graph between V and I from the given data, a straight line is obtained, thus the given data verifies Ohm's law.                                                                                                                                                                          (2)                               Or An electromagnet is a coil of insulated conducting wire wound around a core of suitable material. When electric current passes through it, it behaves like a magnet, its magnetic properties vanish when current is switched off.                                                                                                                                                                                 In scrap yard, it is used to separate magnetic junk material.                                                                                         (1) The strength of an electromagnet can be increased by increasing the number of turns in the coil, increasing magnitude of current and using soft iron core.                                                                                                   It is based on principle of magnetic effect of current.                                                                                                      (1)