## PHYS208 Fundamentals of Physics II

November 16, 1992    Midterm Exam 2

1. a.

• In which direction is the electric field?

into the page (screen)

• (velocity reversed) Is the beam deflected now? If so, in which direction?

particle is deflected into the page (screen)

• Is the electron beam deflected? If so, in which direction?

No deflection

1. b.

• In which direcion in the current induced in loop b?

opposite sense of ia

• What is the direction of the force that loop a exerts on loop b?

down, since the force is repulsive; away from loop a

1. c.

• The emf induced in a circuit is proportional to the rate of change of magnetic flux through the circuit.

• Lenz's law states that the direction of an induced emf is always opposite to the change in magnetic field that induced it.

• The magnitude of a magnetic field varies inversely with the square of the distance from the current element that creates the field.
(Note: I now use the term "current infinitesimal" instead of "current element"; the magnetic field created here is an infinitesimal contribution.

2.  Evaluate the inductance per meter length of RG58/U cable?

0.26 microH/m

3. Evaluate the force per meter length if the separation d is 1.0 mm and both currents are 10 A.

0.020 N/m

4.  What should R be for the lamp to flash every 1.5 sec?

11 megaohm

"http://www.physics.udel.edu/~watson/phys208/exams/mid2-92f-ans.html"
Last updated Nov. 12, 1997.
Copyright George Watson, Univ. of Delaware, 1997.