Register to reply

Current from square wave into inductor in series with cap and resistor in parallel

by thomas49th
Tags: current, inductor, parallel, resistor, series, square, wave
Share this thread:
Apr10-11, 08:52 AM
P: 656
1. The problem statement, all variables and given/known data
In the circuit of Fig. 16(a), the voltage v has the periodic waveform shown in Fig. 16(b) with a period of 4 us and an amplitude of 20 V.

2. Relevant equations

i = Cdv/dt

v = Ldi/dt

3. The attempt at a solution

Assuming that x is constant (at its average value), draw a dimensioned sketch of the waveform
of iL(t) and determine its maximum and minimum values.

x = 5 (as duty cycle is 1/4 => 20/4)
Therefore at begining of cycle v = 20 => inductor has drop of 15v across it

using v = Ldi/dt
di/dt = 15/2e-3
= 7500 Amp per sec
i = 7.5mA

So in one microsecond the current in the inductor goes from 0 to 7.5mA agreed? I've presumed the charge is linear, is this correct? Why?

Now after 1us the v is 0 volts for 3us. This means the inductor's magnetic field will collapse into the capacitor or resistor or both?

Phys.Org News Partner Science news on
'Office life' of bacteria may be their weak spot
Lunar explorers will walk at higher speeds than thought
Philips introduces BlueTouch, PulseRelief control for pain relief
Apr10-11, 01:52 PM
P: 1,781
Nope. The current isn't starting up at zero.

You need to find the average current too (you have a resistor with an average voltage already so this is easy.)

The inductor current won't collapse. It will be a triangle wave up and down with the applied voltage riding on top of a steady DC current.
Apr10-11, 03:17 PM
P: 656
Okay the current to begin with is 20/R = 5/1000 = 5mA. Average current at iR = 5/1000 = 5mA through the resistor. Correct? Why is the shape straight lines (not exponentially stuff)

Apr15-11, 07:41 PM
P: 656
Current from square wave into inductor in series with cap and resistor in parallel


Register to reply

Related Discussions
Bypass current of parallel conected inductor/diode General Physics 0
Current across resistor and inductor Introductory Physics Homework 5
Resistor, capacitor, and inductor in series Introductory Physics Homework 0
Resistor in parallel/series Introductory Physics Homework 9
How to calculate current of a resistor inside of another parallel resistor? Introductory Physics Homework 2