Question

Consider a solenoid oriented on a horizontal surface from north to south. We know that self-induced emf in this solenoid is not zero and directed from south end of solenoid to north end. We can conclude from this fact that current though this solenoid is
a. passing from south end of solenoid to north end and is decreasing in magnitude

b. passing from north end of solenoid to south and and is increasing in magnitude

c. passing from south end of solenoid to north end and is increasing in magnitude

d. there is not enough information given to answer this question

e. passing from north end of solenoid to south end and is decreasing in magnitude

Answer 1

Answer:

a. passing from south end of solenoid to north end and is decreasing in magnitude

Explanation:

by taking into account the Lenz's law

$\epsilon=-\frac{d\Phi_{B}}{dt}$

From the Lenz's law we know that if the self-induced emf is due to a decrease in the current, the self-induced current is in a opposite direction. In the other case, when the current increase, the self-induced current is in the same direction that the initial current in the solenoid.

If we assume the second case (the current is increasing) the change in the magnetic flux is negative and the self-induced current contributes to the initial current

I hope this is usefull for you

regards