# Revision question

hi okay i have a question, it is an old test question so it would be nice is someone ans b4 8am cos that is when the test it but if not that is fine just incase someone is surfing this website at this time.. ha.n e ways the question is a 25mH inductor is connected in series with a 20ohm resisto thru a 15v power supply and a swiitch. if the switch is closed at t= 0 what is the current at t = 7 the ans is 750 but do not know how was derived. thks.

mukundpa
Homework Helper

lurflurf
Homework Helper
hotstuff said:
hi okay i have a question, it is an old test question so it would be nice is someone ans b4 8am cos that is when the test it but if not that is fine just incase someone is surfing this website at this time.. ha.n e ways the question is a 25mH inductor is connected in series with a 20ohm resisto thru a 15v power supply and a swiitch. if the switch is closed at t= 0 what is the current at t = 7 the ans is 750 but do not know how was derived. thks.
What is the current when t=0?
What is the current when t=infinity?
if i(0)<i(7)<i(infinity)
Where in this range do you expect i(7) to be?
What is i'(7)?
How does i(t) evolve over time?