I'm not sure about the magnitude, but the direction of the normal force is upward.
Answer:
Commutator is a ring which reverse the direction of current in AC circuit so that the coil connected to it will continuous to move in the same direction.
Explanation:
In motors there exist a coil which is rotated due to torque of magnetic field when current flow through it. Since AC current is used to run the motor so we know that AC current changes its direction after half cycle.
So here commutator plays an important role to reverse the direction of current after every half cycle so that the current goes in same direction always into the coil.
This will produce a constant direction torque on the coil so that it will rotate in same sense always.
So commutator role is to provide same direction current to the coil by reversing its direction after every half cycle
Answer:
field B = µ₀c I / 2πr
The field in the xy plane due to the fact that the two wires are perpendicular to the plane Bx and By are everywhere 0 on the plane.
a) Midway between, the Bz components cancel, so <0, 0, 0> T
b) Bz = µ₀ x I / 2πa + µ₀ x I / 2π(3a) = (µ₀ x I / 2π)(1/a + 1/3a)
Bz = (µ₀ x I / 2πr)(3/3a + 1/3a) = (µ₀x I / 2πr)(4 / 3a) = 2µ₀ x I / 3πa
c) By symmetry, Bz = -2µ₀ x I / 3πa (that is, down into the plane)
