Examples from The Answer book:   

In a 60 cycle system, what length of time does it take to go 90 degrees?

(a) 1/3 second    (b) 1/90 second    (c) 1/60 second    (d) 1/240 second

Solution: 90/360˚ = .25   60 cycles/.25 = 240 or 1/240 second.


40% is equivalent to _______.

(a) 5/8    (b) 3/5    (c) 2/5    (d) 5/16

* 2/5  = .40 or 40%.


If the resistance is held constant, what happens to the power if the current is doubled?

(a) doubled    (b) halved    (c) multiplied by 4    (d) divided by 4

* Multiplied by 4. W= I2 R  Example: 10 amps x 10 amps x 10 ohms = 1,000 watts
                                                                20 amps x 20 amps x 10 ohms = 4,000 watts



Two 500 watt lamps connected in series across a 120 volt source. The total power consumed is _______ watts.

(a) 1000    (b) 500    (c) 250    (d) 200

R = E2/W 120v x 120v/500w =28.8 ohms x 2 = 57.6 ohms. I = E/R 120v/57.6 Ohms  = 2.0833 amps
W = I2  R 2.0833a x 2.0833a x 57.6 ohms = 250 watts or W = E2/R 120v x 120v / 57.6 ohms =250 watts
                                                               

    How confident are you with math calculations? Do you like to read and do you retain what you read and study? Are you willing to schedule a time to study and make this your #1 priority?
    Closed-book (No Book) exams stimulate deep learning more than open-book exams.

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