- #1
Daltohn
- 30
- 0
Homework Statement
The wire in an electromagnet has the resistance 125 ohms and a parallel resistor has the resistance 4 kiloohms. The magnet is kept magnetized by a DC voltage 40V. What is the voltage over the electromagnet soon after switch K is opened? Also comment on the polarity of the voltage.
Homework Equations
emf=-L(delta I/delta t)
V=IR
The Attempt at a Solution
I have no idea because I'm not able to extract enough data from that text. The polarity should be the same according to Lenz's law. Answer is 2,3 kV.
Please don't use calculus btw, appreciate any help :)