Help with determining the direction of induced currents

[riseofphoenix]

2. Three loops of wire move near a long straight wire carrying a current as in the following figure.

(a) What is the direction of the induced current, if any, in loop A?

a. clockwise
b. counterclockwise
c. No current is induced. (ANSWER)

WHY IS "C" THE ANSWER? I don't understand the concept of determining the direction of an induced current. What does an induced current even mean?? Is it a current caused by something else (such as a long wire in this case)?

(b) What is the direction of the induced current, if any, in loop B?

a. clockwise
b. counterclockwise (ANSWER)
c. No current is induced.

:(:(!

(c) What is the direction of the induced current, if any, in loop C?

a. clockwise (ANSWER)
b. counterclockwise
c. No current is induced.


5. In the figure below what is the direction of the current induced in the resistor at the instant the switch is closed?

a. The current out of the page.
b. No current is present.
c. The current is into the page.

 

[Doc Al]

You need to study up on http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/electric/farlaw.html#c1 and http://hyperphysics.phy-astr.gsu.edu/%E2%80%8Chbase/electric/farlaw.html#c2.

 

[riseofphoenix]

Ohh thanks!

 

[rude man]

2. Three loops of wire move near a long straight wire carrying a current as in the following figure.

(a) What is the direction of the induced current, if any, in loop A?

a. clockwise
b. counterclockwise
c. No current is induced. (ANSWER)

WHY IS "C" THE ANSWER? I don't understand the concept of determining the direction of an induced current. What does an induced current even mean?? Is it a current caused by something else (such as a long wire in this case)?

Faraday: emf = -N d(phi)/dt. Is there a d(phi)/dt for coil A?
phi = B x area of coil.

The others are similarly solved. As Doc Al says, you need Lenz' law to determine direction if a current is induced. Applies to problem 5 also.

b) What is the direction of the induced current, if any, in loop B?[/B]

a. clockwise
b. counterclockwise (ANSWER)
c. No current is induced.

:(:(!

(c) What is the direction of the induced current, if any, in loop C?

a. clockwise (ANSWER)
b. counterclockwise
c. No current is induced.


5. In the figure below what is the direction of the current induced in the resistor at the instant the switch is closed?

a. The current out of the page.
b. No current is present.
c. The current is into the page.

 

[Nickie]

(ANSWER)

WHY IS "C" THE ANSWER?

An induced current is a current that is created in a conductor when it is exposed to a changing magnetic field. This changing magnetic field can be created by a moving magnet, a changing current in a nearby wire, or any other source of changing magnetic field. In this case, the long straight wire carrying a current is the source of the changing magnetic field.

For loop A, the direction of the induced current can be determined by the right-hand rule. If you point your thumb in the direction of the current in the long wire, your fingers will curl in the direction of the induced current in loop A. Since the current in the long wire is going into the page, the induced current in loop A will be counterclockwise.

For loop B, using the right-hand rule again, we can see that the induced current will be clockwise.

For loop C, the induced current will be counterclockwise because the direction of the current in the long wire is opposite to the direction of the current in loop C.

In the second figure, the switch is closed, creating a changing magnetic field in the loop. Using the right-hand rule, we can see that the induced current in the resistor will be into the page. This is because the changing magnetic field created by the closed switch is perpendicular to the direction of the current in the resistor, causing the induced current to flow into the page.

I hope this helps to clarify the concept of induced currents and how to determine their direction using the right-hand rule. It is an important concept in electromagnetism and is used in many applications, such as generators and transformers.