This question works with the concept of induction. Simply put, the current in a wire will adjust such as to oppose a change in magnetic field. The loop originally has a magnetic field pointing away from the observer. Therefore, with the external magnetic field suddenly activated in the opposite direction (towards the observer), the current in the loop will act to counteract this change and increase while remaining clockwise.

This question requires knowlegde of the right-hand rule. Point the fingers of your right hand in the direction of the electron's velocity (to the right). Point your thumb in the direction of the magnetic field (into the page). Your palm should be facing in the direction of the force on a positive particle. However, electrons are negative, so this direction must be reversed, meaning that the direction of the force is upward along the plane of the page.

This is an application of the right hand rule for magnetic fields produced by current carrying loops. To use the right hand rule, put your right thumb in the direction of the current, and the direction of the magnetic field is the same as the way your other four fingers wrap as you close your fist. The answers which include increasing or decreasing of a current hint at the concept of induction and are incorrect. 

Recall that , where . The shape, material characteristics, and resistance do not appear in this equation. So only the size (area) of the loop influences the emf.

First, magnetic field lines, like electric field lines, can never cross. Also, unlike electric field lines, magnetic field lines are continuous—they do not have starting or ending points. Next, the force experienced by a charge in a magnetic field depends on the charge's velocity direction, not just the magnetic field. So the only remaining choice is that magnetic field lines show both the relative strength and direction of the field.

We use the formula for force on a wire in a magnetic field:

Where  = force,  = current,  = length of wire, and  = magnetic mield

A charged particle in a particle accelerator moves in uniform circular motion. The equation for centripetal force caused by uniform circular motion is:

The equation for magnetic force is:

Set the equations equal to each other, and solve for velocity.

The only answer choice that does not correspond to an increase in velocity is increasing the mass of the particles in the accelerator.

When finding the direction of the force on a POSITIVELY charged particle due to a magnetic field, we can use the right hand rule. Holding your thumb perpendicular to the rest of your fingers (as if motioning to stop), orient your fingers parallel to the lines of the magnetic field, and your thumb with the velocity vector of the charge. For a positive charge, the force would be oriented directly out of the palm; HOWEVER, the charge of an electron is negative and therefore the force will be applied in the opposite direction. This would mean that the force would be coming directly out of the backside of your hand (in this case, towards the top of the page) using the right hand rule.

A charged particle's motion in a uniform magnetic field is described by R = mv/qB, so the radius of the particle's path is proportional to its mass. Thus if mass is doubled, radius is also doubled. 

A magnetic force can accelerate a charged particle by changing the direction of its velocity, but cannot change the magnitude of velocity.

If the magnetic field has any components perpendicular to the particle's initial velocity, the particle will experience a force according to the equation:

This force is generated perpendicular to the particle's path and will cause a change in the direction of the particle's velocity. If the magnetic field is parallel to the initial velocity, the particle will experience no magnetic force, and its path will remain unchanged. It is not possible for the particle to accelerate in the magnetic field without changing direction.