Circuit Anlysis & Linear Systems

Question 1

Answer 1

So were are trying to find how much Capacitive Reactive Power (Q) is needed to correct the power factor lag.

First convert complex power from polar to rectangular

Find the pf correction pf:

cos(theta₂) = 0.97

arccos0.97 = theta₂

theta₂ = 14.07 degrees

The new reactive power Q_desired = Ptan(theta₂)

Q_needed = Q_original - Q_desired

Question 2

Answer 2

The rms current is calculated from the peak current by using this equation.

The phase angle is referenced to the voltage waveform.

The current reaches its peak 90 degrees before the voltage. Leading currents have a positive phase shift.

Question 3

What is most nearly the current immediately after the switch is closed?

(A) 0.2 A

(B) 0.7 A

(C) 1 A

(D) 3 A

Answer 3

Question 4

Answer 4

Find the Forcing Frequency

2πf = 2π(60 Hz) = 377 rad/s

Find the imedances of each individual element

Inductor Z_L = j(omega)L = j(377 rad/s)(133 x 10^-3 H) = j50 ohms

Resistor Z_R = R = 100 ohms

Question 5

Answer 5

Find the equivalent resistance and equivalent voltage.

R_eq = 21 ohms

V_eq = 70 V + ( -50 V ) = 20 V

Ohm’s law to determine the current through the circuit.

The voltage across any individual resister is found from ohms law.

V = IR = (0.952 A) (10 ohms) = 9.52 V (9.5 V)

Question 6

Answer 6

Question 7

Answer 7

Pg. 361 of handbook. Use formula.

Make sure units are correct when plugging in information.

Question 8

The voltage across and current through the 5 ohm resistor in the center leg are most nearly….

(A) 2 V and 1 A

(B) 2 V and 3 A

(C) 5 V and 1 A

(D) 5 V and 20 A

Answer 8

Question 9

Answer 9

Question 10

Answer 10

Question 11

Answer 11

Read the entire problem!

V = IR

I_BE = ( V_BE/R) = 60 mA

Question 12

Answer 12

Since this is a DC Circuit, the capacitor blocks current flow. No current will flow through it.

The only voltage source in the loop containing the 5, 10, and 20 ohm resistors is the 100 V battery.

Use Kirchhoffs voltage law for the loop.

B

Question 13

Answer 13

Use Joules Law

P = I²R

Question 14

A Thevenin equivalent circuit and its original resistive load are shown. The 1 ohm load resistance is subsequently changed in order to maximize the power transfer.

Answer 14

Question 15

Answer 15

Question 16

Answer 16

To find formula search “RMS or Effective” in handbook

Question 17

Answer 17

Question 18

Answer 18

Find the reactance of both the capacitor and inductor by using the formulas on pg. 360

Find the magnitude of the impedance

Question 19

Answer 19

When a circuit is purely resistive, the power factor is equal to 1.

Question 20

Answer 20

Pay attention to the formula. Its an unusual way to find power factor.

Question 21

Answer 21

Turns ratio formula pg 363.