15 Questions
Give the magnitude of I, if R = 0.8 Ohms and the magnitude of Vs is 13 V (rounded off to 2 decimal places).
6.55
At what frequency will the reactances of a 3mF capacitance and a 1mH inductance be equal?
577.4 rad/sec
By what angle does i1 lead i2 if i1 = -5cos(ωt) A and i2 = 3sin(ωt - 95°)?
5
The impedance angle of a parallel RC circuit is _____.
Negative
In a pure _____, voltage and current are in phase.
Resistor
A coil with a 240V source has a current of 10.5 A at 60 Hz. What is the inductance (in mH) when the frequency changes to 39 Hz and the current becomes 14.7 A?
55.84
The imaginary component of admittance is _____.
Susceptance
If the reactance of a capacitor at 50 Hz is 47 ohms, what will be the reactance (in ohms) when the frequency is increased to 98 Hz?
23.98
Determine the magnitude of Vo given XC = 4.1 ohms.
4.20
Calculate the magnitude of Vx in the circuit shown. (in Volts)
29.36
In a series RLC circuit with R = 2.7 Ohms, C = 3mF, and L = 1mH, what is the circuit current (in Amperes) for an applied voltage of 5V at 577.4 rad/sec?
1.85
If three impedances of 15 Ohms each are connected in wye configuration, what will be the magnitude of each impedance (in Ohms) when converted to delta?
45
Calculate the reactance (in Ohms) of a 0.19H inductor at 133 rad/sec.
25.27
Determine the susceptance (in Siemens) of a 0.044F capacitor at 575 rad/sec.
25.30
In a series RL circuit connected to a 110-V AC source, if the voltage across the resistor is 18 V, what is the voltage across the inductor (in Volts)?
108.52
Study Notes
Calculating Current and Impedance
- To calculate the magnitude of I, use the formula I = Vs / R, where R is the resistance in Ohms and Vs is the voltage in Volts.
- If R = 0.8 Ohms and Vs = 13 V, the magnitude of I is approximately 6.55.
Reactance and Resonance
- At resonance, the reactance of a capacitor (XC) is equal to the reactance of an inductor (XL).
- If C = 3mF and L = 1mH, the frequency at which their reactances are equal is approximately 577.4 rad/sec.
Phase Angle and Impedance
- The impedance angle of a parallel RC circuit is negative.
- In a pure resistor, voltage and current are in phase.
- The phase angle between two currents can be compared by finding the angle between their sinusoidal functions.
Inductance and Reactance
- The reactance of an inductor (XL) is proportional to the frequency of the AC current.
- If a coil has a 240V source and a current of 10.5 A at 60 Hz, the inductance L can be calculated using the formula XL = 2πfL.
- The inductance L can be approximately 55.84 mH.
Admittance and Susceptance
- The imaginary component of admittance is susceptance.
- Susceptance is the reciprocal of reactance.
- The susceptance of a capacitor can be calculated using the formula B = 1 / XC.
Capacitive Reactance
- The reactance of a capacitor (XC) is inversely proportional to the frequency of the AC current.
- If XC = 47 Ohms at 50 Hz, it becomes approximately 23.98 Ohms at 98 Hz.
Circuit Analysis
- To solve for Vo, the magnitude of the output voltage, use the formula Vo = Vs / (R + jXL).
- To solve for Vx, the magnitude of the voltage across a component, use the formula Vx = Vs / (R + jXC).
- The circuit current can be calculated using the formula I = Vs / Z, where Z is the total impedance of the circuit.
Delta-Wye Conversion
- When converting three impedances from wye to delta, the magnitude of each impedance is multiplied by √3.
- If each impedance is 15 Ohms, the magnitude of each impedance in the delta configuration is approximately 45 Ohms.
Test your knowledge of electrical circuits with these multiple-choice questions covering topics such as circuit analysis, reactance, and impedance.
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