Problems on Self-Induction: UNIZOR.COM - Physics4Teens - Electromagnetism - Self-Induction
Channel: Zor Shekhtman on UNIZOR Education
Date: 16/07/2020

UNIZOR.COM - Physics through a Looking Glass of Mathematician


Notes to a video lecture on http://www.unizor.com

Problems on Self-Induction

Problem A

Consider a wire of resistance R0 bent into a circle of a radius r with its ends connected to a battery producing a voltage U0.
There is a switch that can turn the flow of electricity in this circuit ON or OFF during a short time period T.
When it turns ON, the resistance of the circuit, as a function of time R(t), changes from infinitely large value to the value of R0 as
R(t) = R0·T/t
When it turns OFF, the resistance changes from the value of R0 to an infinitely large value as
R(t) = R0·T/(T−t)
What is the EMF of self-induction Ui during the current switching ON or OFF?




Problem B

In the same setting as in Problem A calculate minimum time Tmin of switching a circuit OFF in order for the current in a circuit grow no more then 10% from the theoretical value I0 = U0 /R0.