Re: Time constant

Would you say this is correct then and the formulas and the units of calculation??

A coil of inductance 4H and resistance of 80Ω is connected in parallel with a 200Ω of resistor of negligible inductance across a 200v dc supply. The switch connecting these to the supply is then opened; the coil and resistor remain connected together. State in each case one for immediately before and one for immediately after opening the switch;

The current Through the resistor

Switch closed
200v/200Ω =1a...

Hi folks I was wondering if someone can help me with some revision questions, that I need the answer and the exponential formulas, it would be a great help. My exams in a couple of weeks and I really needed to learn this stuff.

1. A coil of inductance 4H and resistance of 80Ω is connected in parallel with a 200Ω of resistor of negligible inductance across a 200v dc supply. The switch connecting these to the supply is then opened; the coil and resistor remain connected together. State in each case one for immediately before and one for immediately after opening the switch;...