Question

A very long, straight wire carries a current of 13.9 A out of the screen. An electron outside the wire is 1.17 cm to the right of the central axis of the wire and is moving with a speed of 4.25×10⁶ m/s.

a. Find the magnitude of the magnetic force on the electron if it is moving directly away from the wire (i.e., rightward).

b. Find the magnitude of the force on the electron if it is moving parallel to the wire in the direction of the current (i.e., out of the screen).

c. Find the magnitude of the force on the electron if it is moving upward.

Answer 1

Here ,

for the magnetic field at the location of the electron

B = u0 * I/(2pi * d)

B = 4pi *10^-7 * 13.9/(2pi * 0.0117)

B = 2.37 *10^-4 T

the magnetic field is 2.37 *10^-4 T

a) when the electron is moving away from wire , as it moving perpendicular to the magnetic field

magnitude of magnetic force = 2.37 *10^-4 * 1.602 *10^-19 * 4.25 *10^6

magnitude of magnetic force = 1.61 *10^-16 N

b)

for out of screen

as it moving perpendicular to the magnetic field

magnitude of magnetic force = 2.37 *10^-4 * 1.602 *10^-19 * 4.25 *10^6

magnitude of magnetic force = 1.61 *10^-16 N

c)

as it is moving parallel to magnetic field

magnitude of force acting on the electron = ZERO