# Md.2ca…Physics Electricity and Magnetism

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Md.2ca…Physics Electricity and Magnetism

1. (Rev 9/11) Two alpha particles, each with a charge of 3.20*10-19 C, are one Ångström (1 x 10-8 cm) apart, in vacuum. What is the electrostatic force acting between them, in N? Is the force attractive or repulsive?

2. (Rev 2/11) If the force acting between two electrons (each with a negative charge of 1.602 x 10-19 C) is 3.8×10-9 N, then what is the electrical permittivity of the medium in which they are embedded? As in the problem above, the two electrons are one Ångström (1 x 10-8 cm) apart.

3. An electron travels in a horizontal (x-y) plane and experiences a force in the vertical (z) direction due to a uniform magnetic field. (The force can be up or down.) Which are the possible directions for the magnetic field? Explain using the right hand rule.

4. (Rev 2/11) What is the magnetic field strength, in Teslas, one centimeter away from a long, straight electric wire carrying a current of 100A?

5. (Rev 5/11) A long straight wire carrying a current of 10 mA is immersed in a 5 T magnetic field.

• The magnetic field lines are perpendicular to the wire. What is the Lorenz force acting on the wire, in N per meter?
• The magnetic field lines are parallel to the wire. What is the Lorenz force acting on the wire, in N per meter?

## Case Assignment Expectations:

In general, Cases are expected to possess the attributes of precision, clarity, breadth, depth, and critical thinking. Not all of these are relevant to the answer to every problem in the case. When it is relevant, the evidence for each attribute is as follows.

• Precision: Numerical answers are calculated correctly, to the correct number of significant figures.
• Clarity: The problem is restated in its simplest form. Relevant variables are identified. Formulas are algebraically rearranged, as necessary. All the mathematical steps are shown, in logical order.
• Breadth: Where discussion is required, the question is placed in context. Alternatives are considered.
• Depth: Where discussion is required, the question is examined in detail. No relevant aspect of the question is omitted.
• Critical thinking: The correct analytical approach is selected. Relevant data areidentified and irrelevant data are ignored. When required, the practical importance of the principle or phenomenon is accurately described.