# I just want to make sure I got the right answers for these two questions...?

1)If a current of 6A/s in one coil induces a 3V potential in another coil, what is the mutual inductance? I got 0.5 H

2)An ideal transformer connects a 120-V source to a 12-V, 1-A load. The secondary has 90 turns. Determine the number of turns in the primary, which I got 108. And determine the source current which I think is 10A but i'm not sure...

steveschoen | College Teacher | (Level 1) Associate Educator

Posted on

Hi, t4,

For these two, the first one look alright to me.  But, the second one. . .

The turn ratio = voltage ratio, or:

primary turns/secondary turns = primary voltage/secondary voltage

So, we would have
:

x/90 = 120/12

Solving this for x, we get x = 900 turns.

But, then, for the current, the proportion is a bit different.  It is:

primary turns/secondary turns = secondary amps/primary amps

For this, plugging in the numbers, we get:

900/90 = 1/x

Solving this for x, we get x = 0.1 amps

Good luck, t4, I hope this helps.

Till Then,

Steve