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Rewa S.
PhD Student at Stanford University
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Physics (Electricity and Magnetism)
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Question:

An infinitely long wire carries electric current pointing out of the page. In which direction does the magnetic field point.

Rewa S.

Using the right hand rule, with my thumb facing the direction of the current and my fingers rotating in the direction of the magnetic field, I get that the magnetic field points counter-clockwise.

Calculus
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Question:

Find the limit of: $$lim_{x ->2} \frac{x-2}{x^2-4}$$

Rewa S.

This problem can be solved in two ways. One method requires the use of L'Hopital's rule because plugging in the limit value gives a result of $$\frac{0}{0}$$. First, take the derivative of the numerator and denominator of the fraction respectively: $$lim_{x ->2} \frac{1}{2x}$$. Plugging in the limit value now results in $$\frac{1}{4}$$, which is the answer. The second method uses simplification. First factor the denominator to $$(x+2)(x-2)$$. Then cancel the $$(x-2)$$ in the numerator with the same phrase in the denominator. This leaves $$\frac{1}{x+2}$$ resulting in the same answer as before.

Electrical Engineering
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Question:

What does the Fourier Transform of a sin wave look like?

Rewa S.

The Fourier Transform of a sin wave is an upward pointing Dirac Delta function on the positive x axis and a downward pointing Dirac Delta on the negative x axis.

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