Question
Sat May 21, 2011 By:

two wires A and B are of the equal length, different cross sectional areas and made of same metal. Q. Name the property which is same for both the wires. Q Name the property which is different for both the wires. Q If the resistance of wire A is 4 times the resistance of B, calculate the ratio of cross section area of wires. Q ratio of radii of the wire.

Expert Reply
Sat May 21, 2011

Resistance  ( R )  of  a  conductor  varies  directly  as  its  length  ( l )  and  inversely  as  its  cross - sectional  area  ( A )  at  a  given  temperature.
Therefore Resistance will be different for both the wires.
where  the  constant   ?   is  known as  the  resistivity  of  the material.  Its  value  depends  on  the  type,  temperature  and  the  pressure  existing  on  the  given  conductor.  Its  unit  is  ohm-meter   ( ? m )
Therefore the two reristance have the same resistivity.
Let the cross section area of wire A be D and cross section area of B be E, then ratio of the cross section area of wires is
And the ratio of radii of the wire is
 
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