1) Which statements about the force on a charged particle placed in a magnetic field are true?
a) A magnetic field always exerts a force on a charged particle.
b) The direction of the force is along the magnetic field.
c) The force is a maximum if the particle is moving in the direction of the field.
d) The force causes the particle to gain kinetic energy.
e) A magnetic force is exerted only if the particle is moving.
2) A 42-cm-long solenoid, 1.8?cm in diameter, is to produce a 0.030-T magnetic field at its center. If the maximum current is 4.6 A , how many turns must the solenoid have?