An electric current is created in a long thin wire. how will increasing the current and changing the direction of the current effect the direction that a compass placed under the wire will point?
a)
it compass will spin continuously.
b)
the compass will flip exactly 180 degrees.
c)
the compass will spin exactly 360 degrees.
d)
the compass will not react and still point north.

The correct answer is B.

Explanation:

When the current is flowing through the vertical wire then the compass needle will points perpendicular to the wire.

When the direction of the electric current is reversed then the direction of the compass needle will also get reversed as the polarity of the magnetic field is changed.

An electric current is created in a long thin wire. When the current will increase and the direction of the current is changed then the compass will flip exactly 180 degree.

Therefore, the correct answer is B.

two charges are fixed in place on the x-axis as shown. the charge at x = 0 is negative and has magnitude q = 2 μcoulombs (1 μcoulomb = 10-6 coulombs). the charge at x = d, (d = +12 cm), is positive and has magnitude q = 4 μcoulombs. find a point x = xo along the x-axis at which the electric field is zero.