Day 20: Sinusoids and Phasors

**This week, I was absent for the choir trip I had to Canada. This is my synthesis of the notes posted online, and my working through of problems my group has on their blog.**

Today was a day with lots of examples (which was lovely to miss...), but I was able to work through all the examples and understand what was going on.


1. First, we looked at a problem Mason made up on his white-board, where we wrote the equation for a sine graph, then shifted it over by .0012.

2. Calculate the phase angle between v 1 = − 10 cos(ωt + 50°) and v 2 =12 sin(ωt − 10°). State which sinusoid is leading.

3. Evaluate the complex number: (30, 30° - (-20, 70°))^-1

4. In this example, we were given four different sinusoidal voltages and asked to convert them into phasor form.

5. Find the sinusoids represented by these phasors: (a) V = j8e−j20o, (b) I = − 3 + j4

6. If v 1 = − 10 sin(ωt + 30o) and v 2 = 20 cos(ωt − 45o), find V = v 1 + v 2 .

7. The voltage v = 12 cos(60t + 45o) is applied to a 0.1-H inductor. Find the steady-state current through the inductor.