# solenoid question (1 Viewer)

#### akkjen

##### Active Member
hi guys, in this experiment how do you know whether the first peak in the graph is positive or negative? thanks

#### TheOnePheeph

##### Active Member
The south pole is going in first, and you want to use Lenz's Law to reverse that change in flux, so you can imagine a magnet inside the solenoid with south pole facing upwards to oppose the change. Using the fact that the magnetic field goes from the north to south pole, you can use right hand grip rule to show the current travels clockwise around the solenoid, therefore coming into the voltage probe from the negative end and producing a negative peak at first.

#### akkjen

##### Active Member
The south pole is going in first, and you want to use Lenz's Law to reverse that change in flux, so you can imagine a magnet inside the solenoid with south pole facing upwards to oppose the change. Using the fact that the magnetic field goes from the north to south pole, you can use right hand grip rule to show the current travels clockwise around the solenoid, therefore coming into the voltage probe from the negative end and producing a negative peak at first.
thanks!!1