An electron has an initial velocity to the south but is observed to curve upward as the result of a magnetic field. This magnetic field must have a component: a) north
b) upwards
c) downwards
d) east
e) west

e) west

Explanation:

According to Lorentz left hand rule, the left hand is used to represent the motion of an electron in a magnetic field. Hold out the left hand with the fingers held out parallel to the palm, and the thumb held at right angle to the other fingers. If the thumb represents the motion of the electron though the field, and the other fingers represent the direction of the field, then the palm will push in the direction of the force on the particle.

In this case, if we point the thumb to the south (towards your body), with the palm facing up, then the fingers will point west.

grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered