Help with determining the direction of induced currents

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Homework Help Overview

The discussion revolves around the concept of induced currents in loops of wire situated near a long straight wire carrying a current. Participants are exploring the direction of induced currents in various loops based on the principles of electromagnetic induction.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand why no current is induced in loop A and seeks clarification on the meaning of induced current. They reference Faraday's law and express confusion about the application of Lenz's law for determining the direction of induced currents.

Discussion Status

Some participants have provided links to external resources for further study. The discussion includes attempts to clarify the principles involved, but there is no explicit consensus on the interpretations of the induced currents in the loops.

Contextual Notes

Participants are working within the constraints of a homework assignment that requires understanding the behavior of induced currents without providing complete solutions. There is an emphasis on the need for conceptual understanding rather than direct answers.

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

20-p-009.gif


(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?

20-p-014.gif


a. The current out of the page.
b. No current is present.
c. The current is into the page.
 
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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.
 
Ohh thanks!
 
riseofphoenix said:
2. Three loops of wire move near a long straight wire carrying a current as in the following figure.

20-p-009.gif


(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?

20-p-014.gif


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

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