107125_1_hw11 by xiaoyounan

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• pg 1
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Question 1

A square loop of wire is rotating around its vertical axis in a magnetic field of
strength B = 0.06 T as shown in View A. The angular frequency of rotation is =
50 rad/s and the loop has a resistance of R = 5 . The length of one side of
the square loop is W = 0.05 m. At the instant of time when the normal to the
loop makes an angle of = 30 with respect to the B field, as shown in View B
where 'N' represents the normal, calculate the current flowing in the loop. Note:
View A would be the side view if            = 90 or 270 .

Enter
I=                  A

Question 2

A 195 turn coil has an area of 4.9 cm2 and rotates in a magnetic field
of 0.5 T.

(a) What frequency will generate a maximum emf of 10 V?

Enter
Hz
[5 points]   0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]
(b) If the coil rotates at 60 Hz, what is the maximum emf?

Enter
V

Question 3

A circuit breaker is rated for a current of 15 A rms at a voltage of 240 V
rms.

(a) What is the largest value of Imax that the breaker can carry?

Enter
A
[5 points]   0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

(b) What average power can be supplied by this circuit?

Enter
W

Question 4

An inductor has a reactance of 115 ohm at 80 Hz.

(a) What is its inductance?

Enter
H
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[after that, multiply credit by 0.5 up to 10 attempts]

(b) What is its reactance at 180 Hz?

Enter
ohm

Question 5

At what frequency would the reactance of a 11 F capacitor equal that
of a 1.4 mH inductor?

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Hz
Question 6

At what frequency is the reactance of a 3 F capacitor 20000 ?

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Hz

Question 7

Four resistors (R1 = 60 Ohms, R2 = 220 Ohms, R3 = 330 Ohms, and R4 = 480
Ohms), an ideal inductor (L = 8 mH), and a capacitor (C = 250 microF) are
connected to a battery (V = 9 V) through a switch as shown in the figure below.

The switch has been open for a long time before it is closed at t = 0. What is
Ustored, the total stored energy in the circuit elements (not including the battery)
a long time after the switch is closed?

Enter
Ustored =                   J

Question 8

True or false:

(a) An RLC circuit with a high Q factor has a narrow resonance curve.

1.        true
2.        false
Enter

[3.33 points]    0 attempt(s) made (maximum allowed for credit = 1)

(b) At resonance, the impedance of a series RLC circuit equals the
resistance R.

1.       true
2.       false

Enter

[3.33 points]    0 attempt(s) made (maximum allowed for credit = 1)

(c) At resonance, the current and generator voltage are in phase.

1.       true
2.       false

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Question 9

A 5 F capacitor is charged to 35 V and is then connected across a
9-mH inductor.

(a) How much energy is stored in the system?

Enter
J
[3.33 points]    0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

(b) What is the frequency of oscillation of the circuit?

Enter
Hz
[3.33 points]    0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

(c) What is the maximum current in the circuit?
Enter
A

Question 10

A resistance R and a 2.7-H inductance are in series across a 60-Hz
ac voltage. The voltage across the resistor is 34 V and the voltage
across the inductor is 23 V. Assume that all voltages in this problem
are rms voltages.

(a) What is the resistance R?

Enter
ohm
[5 points]   0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

(b) What is the ac input voltage?

Enter
V

Question 11

A series RLC circuit with L = 12 mH, C = 3.9 F, and R = 3.6 is driven
by a generator with a maximum emf of 100 V and a variable angular
frequency .

(a) Find the resonant (angular) frequency                0.

Enter
[1.43 points]     0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

(b) Find Irms at resonance.

Enter
A
[1.43 points]     0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

When the angular frequency = 8950 rad/s,
(c) Find the capacitive reactance XC in ohms.

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[1.43 points]     0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

Find the inductive reactance XL in ohms.

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[1.43 points]     0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

Enter

[1.43 points]     0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

Find Irms.

Enter
A
[1.43 points]     0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]

(e) Find the phase angle (in degrees).

Enter
degrees

Question 12

The primary of a step-down transformer has 215 turns and is
connected to a 120 V rms line. The secondary is to supply 29 A at 6 V.

(a) Find the current in the primary.

Enter
A
[5 points]   0 attempt(s) made (maximum allowed for credit = 5)
[after that, multiply credit by 0.5 up to 10 attempts]
(b) Find the number of turns in the secondary, assuming 100%
efficiency.

Enter

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