Lenz's Law

[Nephix]

Hey guys how's it going.

Just a quick question on how to interpret Lenz's law with something like question 14 from VCAA 2007 Exam 2.

Could anyone help me determine in which way induced current will be relative to the flux it creates?

Thanks, good luck for the exam!

[Alwin]

Hey guys how's it going.

Just a quick question on how to interpret Lenz's law with something like question 14 from VCAA 2007 Exam 2.

Could anyone help me determine in which way induced current will be relative to the flux it creates?

Thanks, good luck for the exam!

Okay, there are two methods to approach Lenz's Law questions.
The first and more popular one goes as follows:

1. Using the right hand grip rule we ascertain that the field induced by the solenoid is to the left
2. Since the switch is closed, the field is increasing to the left
3. Thus, the induced current must cause a field increasing to the right or decreasing to the left
4. We choice the former option and use the grip rule again where our thumb points to the right
5. Thus, the current flows from Y to S
6. But it only flows momentarily because current is only induced when there is a change in magnetic flux, ie when the switch is opened or closed

Second method (I personally prefer) goes like this:
1-2 same
3. Field going to the left, so a north pole at the left end of the solenoid and a south pole at the other
4. As the solenoid is being switched on, it's like pushing a S-pole towards the second loop
5. To oppose this, a S-pole should be induced in the end closest to the S-pole of the solenoid, so magnetic field is to the right
5-6 from above

Hope it helps

[Nephix]

Awesome, thanks for that dude =D