Question

how will the resistance of wire change when its length doubled ?its diameter is doubled?and its temperature is increased ?

Answer 1

Let the original resistance be R.We know,R is directly proportional to length of the wire L,and inversely proportional to the area of cross section of the wire A. (i)When length is doubled,thr original resistance R becomes 2R,i.e.,the resistance also doubles. (ii)When diameter is doubled,the area of the wire becomes 4 times the original area.Hence new resistance becomes 1/4th of original R;since R is inversely related to the area A. (iii)The resistance of a typical conducting wire is low when temperature is low and high when temperature is high.Therefore,when the temperature is increased,resistance increases