The discussion focuses on determining the direction of current in two parallel wires and the behavior of a neutral point in a magnetic field. The current, I, flows in the same direction in both wires, creating magnetic fields that interact at point P, which is closer to wire R. When I is increased, the neutral point P moves towards wire R due to the stronger magnetic field created by wire R. Additionally, a second neutral point exists to the left of wire Q, as the fields from both wires must counterbalance the uniform magnetic field present.
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But you said that B doesn't equal to zero, and now you say that the combined field from the wires cancels the uniform field.Doc Al said:When the current is increased, you need to also increase r if you want to keep the B constant.
But we have two wires to worry about. We're trying to find the point where the combined field from the wires cancels the uniform field. It used to be point P, but then they went and increased the current on us.
Closer to R?Doc Al said:Good! So which direction will the new 'neutral point' be?
The B from the two wires doesn't equal zero.moenste said:But you said that B doesn't equal to zero
That's right.moenste said:and now you say that the combined field from the wires cancels the uniform field.
Just the opposite. The field from the wires is proportional to I * (1/rQ - 1/rR). Since I is increasing, and we want B to remain the same, we need (1/rQ - 1/rR) to decrease.moenste said:Closer to R?
1 / 0.8 - 1 / 0.2 = - 3.75Doc Al said:Just the opposite. The field from the wires is proportional to I * (1/rQ - 1/rR). Since I is increasing, and we want B to remain the same, we need (1/rQ - 1/rR) to decrease.
That's true, but we want that factor to decrease, not increase.moenste said:If we want it to increase, we need to increase the distance from Q. Therefore P goes closer tto R.
Thank you, I think somehow I got it.Doc Al said:That's true, but we want that factor to decrease, not increase.