Conceptual Questions Lenz's Law, Solenoid

[devilaudy]

Homework Statement

https://www.dropbox.com/s/17hsoz0zdfoston/Screen shot 2013-05-10 at 12.37.44 PM.png

1) A voltage is applied to a solenoid such that a current is flowing in the indicated direction. Inside the solenoid is a single wire loop that is oriented in the same direction as the solenoid windings.

Which one of the following statements is true in the case where the voltage applied to the solenoid is increased?
a) The magnetic field of the solenoid points to the left while the induced current at location A points out of the paper.
b) The magnetic field of the solenoid points to the right while the induced current at location A points into the paper.
c) The magnetic field of the solenoid points to the left while the induced current at location A points into the paper.
d) The magnetic field of the solenoid points to the right while the induced current at location A points out of the paper.

2) Which one of the following statements is true in the case where the voltage applied to the solenoid is increased?
a) The magnetic dipole moment of the loop points to the right.
b) The torque on the loop points into the paper.
c) The torque on the loop points out of the paper.
d) The magnetic dipole moment of the loop points to the left.
e) A voltage is only induced in the inner loop, not in the solenoid itself.

Homework Equations

Lenz's law

The Attempt at a Solution

I thought the answer to question 1 was c) since the magnetic field would point in the opposite direction to fight the increase in magnetic flux, but it was wrong. I have no idea where to start for the second question. Thanks in advance!

 

[barryj]

A to part 1, wrap your hand around the wire around the solonoid. Where do the fingers point?

 

[devilaudy]

To the right. I know how to use the right hand rule, but in this situation I am confused with the loop inside the solenoid. The magnetic field inside the solenoid points to the right, but how does that affects the current inside the loop? Would the current at location A point outside the paper?

 

[barryj]

What does Lenz law state? Something like the current would oppose the change in the field?

 

[Nickie]

I can provide a response to the following content by explaining the concepts of Lenz's Law and Solenoids. Lenz's Law states that the direction of an induced current will be such that it opposes the change that caused it. This means that when a voltage is applied to a solenoid and the current is flowing in a certain direction, the induced current will flow in the opposite direction to resist the change in magnetic flux.

In the first question, the correct answer is d) The magnetic field of the solenoid points to the right while the induced current at location A points out of the paper. This is because when the voltage is increased, the magnetic field of the solenoid will also increase in the same direction, and the induced current will flow in the opposite direction to oppose this change.

In the second question, the correct answer is c) The torque on the loop points out of the paper. This is because when the voltage is increased, the induced current will create a magnetic field that interacts with the magnetic field of the solenoid, causing a torque on the loop. The torque will be in the direction that opposes the increase in magnetic flux, which is out of the paper.

Additionally, it is important to note that a voltage will also be induced in the solenoid itself, not just in the inner loop. This is because the changing magnetic field created by the induced current in the loop will also affect the magnetic flux in the solenoid, causing a voltage to be induced in it as well.

I hope this explanation helps in understanding the concepts of Lenz's Law and Solenoids. It is important to always consider the direction of induced currents and magnetic fields when dealing with changes in voltage and magnetic flux.