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1) Two wires parallel to each other and seperated by a distance d carry differen

ID: 1490758 • Letter: 1

Question

1) Two wires parallel to each other and seperated by a distance d carry different currents; they exert a force with magnitude F on each other. (a) The wires carry current in the same direction. If the current carried by both wires is divided by three and the distance between the wires is divided by three, then what will the force's magnitude be (as a multiple of F) and will it be repulsive or attractive?

2) The wires carry current in opposite directions. If the current carried by one of the wires is divided by five and the distance between the wires is divided by three, then what will the force's magnitude be (as a multiple of F) and will it be repulsive or attractive?

Explanation / Answer

the magnetic force between the wires is

F = uo I1 I2 L/ 2 pi d

for first wire

F1 = uo I1 I2 L/ 2 pi d

the new force

F2 = uo (I1/3) (I2 /3) L/ 2 pi (d/3)

= 0.333F1

attractive

(2)

F2 = uo (I1/5) (I2 ) L/ 2 pi (d/3)

= 0.6F1

repulsive