Current of Electricity and Emf questions?

Dec 2013
Can anyone help me with the following 2 questions.
For the 1st question, I have no idea how to begin with it?
For the 2nd one, it is either A or B but what is the difference? The field line still cuts the plane of the coil??


PHF Hall of Fame
Apr 2008
For the first question, the hint is resistance is proportional to the length if the material is the same. You have to calculate the resistance for segments 2x, x/2. Then you can sum up the resistance between p and q. But before summing up please try to draw the lines as individual resistors and calculate the equivalent resistance.

For second question, take note that the distance of the coil from the wire is large in B than A. Try to look for the equation that helps you to calculate the induced emf
Dec 2013
I still dont get it for the first question? What is the steps to calculate the overall resistance between P and Q? Can you show me the working?


PHF Helper
Jun 2010
Morristown, NJ USA
The reistance of each section is proportional to its length (the longer it is the higher the resistance) and inversely proportional to its area (the thinner it is, the higher the resistance). Since the right hand piece is twice as long as the left and half the cross-section area that means its resistance is 2/(1/2) = 4 times the resistance of the left piece. The total resistance from P to Q is the sum of the resistances of the two pieces.
Oct 2013
What is the steps to calculate the overall resistance between P and Q?