I will raise the Karma points awarded if you tell me how to raise it to what you
ID: 2018553 • Letter: I
Question
I will raise the Karma points awarded if you tell me how to raise it to what you feel is appropriate for these answers.I will rate Lifesaver if shown how the answer was achieved. Thank you for your time.
1. Two electrons, each with a charge of -1.602*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. If the force acting between the two electrons in problem 1 is 3.8x10-9 N, what is the electrical permittivity of the medium in which they are embedded?
3. An electron travels along the x-axis in a horizontal (x-y) plane, in the positive direction. It experiences a force in the vertical (z) direction due to a uniform magnetic field. (The force can be either up or down.) Which are the possible directions for the magnetic field? Explain using the right hand rule.
4. What is the magnetic field strength, in Teslas, one cm from a long, straight electric wire carrying a current of 100A?
5. A long straight wire carrying a current of 10 mA is immersed in a 5 T magnetic field. 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 are identified and irrelevant data are ignored. When required, the practical importance of the principle or phenomenon is accurately described.
Explanation / Answer
1. F = kq1q2/r^2 = (9*10^9Nm^2/C^2)*(-1.602*10^-19C)^2/(1*10^-10m)^2 = 2.31*10^(-8)N
The force is repulse; two like charges repel each other.
2. F = kq1q2/r^2, where k=1/(40). This formula is for a vacuum. If in a media, use
F = q1q2/(4r^2), where is the permittivity in that media), so
= 4Fr^2/q1q2 = 4(3.8*10^-9N)(1*10^-10m)^2/(-1.602*10^-19C)^2 = 1.86*10^10 F/m
3. If the force is upwards, then the magnetic field has to be in the negative y direction, and the opposite for if the force is downwards. This is because the electron is negative, don't forget.
4. B = 0I/(2r) = (4*10^-7 N/A^2)*(100A)/(2(0.01m)) = 0.002 T
5. F = IlB (current * length * B, just to be clear), so F/l = I*B = (10^-3 A)*(5T) = 5mT = 5*10^-3 N/m