2 . F = qvB sin θ .3 . Magnetic flux is BA , so the units are tesla·meters^2 (or, alternatively, webers). EMF is a voltage, so
the units are volts.
4 . Point your right thumb in the direction of the current, i.e., to the left. Your fingers point in the
direction of the magnetic field. This field wraps around the wire, pointing into the page above the
wire and out of the page below the wire. Since point P is below the wire, the field points out of the
page.
5 . This equation is only valid when a point charge produces an electric field. (Careful—if you just said
“point charge,” you’re not entirely correct. If a point charge experiences an electric field produced by
something else, this equation is irrelevant.) It is an equation for the electric field produced by the
point charge.6 . Do not use E = kQ /r 2 here because the electric field is known. So, the source of the electric field is
irrelevant—just use F = qE to find that the force on the charge is (1 C)(100 N/C) = 100 N. (The
charge is placed at point P , so anything happening at point Q is irrelevant.)
7 . Yes! Induced EMF depends on the change in flux. So, imagine that the flux is changing rapidly from
one direction to the other. For a brief moment, flux will be zero; but flux is still changing at that
moment. (And, of course, the induced current will be the EMF divided by the resistance of the wire.)
8 . False. The negative particle will be forced to the left. But the particle could have entered the field
while moving to the right ... in that case, the particle would continue moving to the right, but would
slow down.
9 . Electric field is a vector, so fields produced in different directions can cancel. Electric potential is a
scalar, so direction is irrelevant.10 . Voltage across resistors in parallel must be the same for each.
Current through resistors in series must be the same for each.
Voltage across capacitors in parallel must be the same for each.
Charge stored on capacitors in series must be the same for each.
11 . The positively charged proton will accelerate with the field, to the right.
The positively charged positron will accelerate with the field, to the right.
The uncharged neutron will not accelerate.
The negatively charged anti-proton will accelerate against the field, to the left.
12 . Use the right-hand rule for each:
The positively charged proton will accelerate into the page.
The positively charged positron will accelerate into the page.
The uncharged neutron will not accelerate.
The negatively charged anti-proton will accelerate out of the page.
13 . If you know the electric potential experienced by the charge, PE = qV .
What Do I Know, and What Don’t I Know?
I’ll bet you didn’t get every question on both of these fundamentals quizzes correct. That’s okay. The