Join thousands of students who trust us to help them ace their exams!Watch the first video
Multiple Choice
An AC source operates at a maximum voltage of 60 V and is connected to a 0.7 mF capacitor. If the current across the capacitor is i(t) = iMAX cos[(100 s−1 )t], a) What is iMAX? b) Draw the phasors for voltage across the capacitor and current in the circuit at t = 0.02 s. Assume that the current phasor begins at 0°.
A
a) imax = 4.2A b) θiC = 115o θVC = 185o
B
a) imax = 4.2A b) θiC = 185o θVC = 115o
C
a) imax = 4.2A b) θiC = 115o θVC = 25o
D
a) imax = 4.2A b) θiC = 25o θVC = 115o
Verified step by step guidance
1
Identify the given values: maximum voltage (Vmax) = 60 V, capacitance (C) = 0.7 mF, angular frequency (ω) = 100 s⁻¹.
Use the formula for capacitive reactance: Xc = 1 / (ωC). Substitute the given values to find Xc.
The maximum current (iMAX) can be found using Ohm's Law for AC circuits: iMAX = Vmax / Xc. Substitute the values of Vmax and Xc to find iMAX.
To draw the phasors, note that the current leads the voltage across a capacitor by 90 degrees. At t = 0.02 s, calculate the phase angle for the current using θiC = ωt.
For the voltage phasor, use the relationship θVC = θiC + 90°. Draw the phasors with the current phasor starting at 0° and the voltage phasor leading by 90°.