Moving Charges ...

If we want to  maximise the magnitude of the magnetic force acting on a charged particle moving in a magnetic field. By which of the following statements we can maximise it.
I. Maximize the strength of the magnetic field
II. Minimize the velocity of particle.
III. Ensure that the particle is moving in the same direction as the magnetic field lines

A charged particle is moving in a circular orbit in a magnetic field. If the strength of the magnetic field becomes four times, Find out the change in radius of the particle's orbit.

A particle with velocity $$2\times10^4m/s$$ enters the uniform magnetic field perpendicularly. Calculate the magnitude of the magnetic force on this particle if charge of particle is -0.04 C and magnetic field of strength is B= 0.5 T.

A positively charged particle is moving in uniform circular path due to magnetic force in uniform magnetic field.Which of the following changes could cause the radius of the circular path to decrease?

A negatively charged particle is moving in a circular path in the clockwise direction in a uniform magnetic field, parallel to the plane of the page. Find out the direction in which magnetic field lines point?

A charged particle is moving in a circular orbit in a magnetic field. If the strength of the magnetic field doubles, how does the radius of the particles orbit change?

Two wires carry current in opposite directions. Which of the following graphs represents the magnetic force acting on each wire? 

Which of the following is not a possible trajectory of a charged particle in a uniform magnetic field? 

What should one do to maximize the magnitude of the magnetic force acting on a charged particle moving in a magnetic field? 
I. Maximize the strength of the magnetic field 
II. Minimize the particles velocity 
III. Ensure that the particle is moving in the same direction as the magnetic field lines.

Two positively charged particles, one twice as massive as the other, are moving in the same circular orbit in a magnetic field. Which law explains to us why the less massive particle moves at twice the speed of the more massive particle?