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If a North pole moves toward the loop from above the page, in what direction is the induced current? 1) clockwise 2) counterclockwise 3) no induced current.

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Presentation on theme: "If a North pole moves toward the loop from above the page, in what direction is the induced current? 1) clockwise 2) counterclockwise 3) no induced current."— Presentation transcript:

1 If a North pole moves toward the loop from above the page, in what direction is the induced current? 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.2a Moving Bar Magnet I

2 If a North pole moves toward the loop from above the page, in what direction is the induced current? 1) clockwise 2) counterclockwise 3) no induced current into the page larger out of the pagecounterclockwise The magnetic field of the moving bar magnet is pointing into the page and getting larger as the magnet moves closer to the loop. Thus the induced magnetic field has to point out of the page. A counterclockwise induced current will give just such an induced magnetic field. ConcepTest 23.2a Moving Bar Magnet I Follow-up: What happens if the magnet is stationary but the loop moves?

3 If a North pole moves toward the loop in the plane of the page, in what direction is the induced current? 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.2b Moving Bar Magnet II

4 no magnetic flux through the loop induced current is zero Since the magnet is moving parallel to the loop, there is no magnetic flux through the loop. Thus the induced current is zero. If a North pole moves toward the loop in the plane of the page, in what direction is the induced current? 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.2b Moving Bar Magnet II

5 ConcepTest 23.1a Magnetic Flux I In order to change the magnetic flux through the loop, what would you have to do? 1) drop the magnet 2) move the magnet upward 3) move the magnet sideways 4) only (1) and (2) 5) all of the above

6 any direction Moving the magnet in any direction would change the magnetic field through the loop and thus the magnetic flux. ConcepTest 23.1a Magnetic Flux I In order to change the magnetic flux through the loop, what would you have to do? 1) drop the magnet 2) move the magnet upward 3) move the magnet sideways 4) only (1) and (2) 5) all of the above

7 1) tilt the loop 2) change the loop area 3) use thicker wires 4) only (1) and (2) 5) all of the above ConcepTest 23.1b Magnetic Flux II In order to change the magnetic flux through the loop, what would you have to do?

8 1) tilt the loop 2) change the loop area 3) use thicker wires 4) only (1) and (2) 5) all of the above  = B A cos  changing the area tilting the loop Since  = B A cos , changing the area or tilting the loop (which varies the projected area) would change the magnetic flux through the loop. ConcepTest 23.1b Magnetic Flux II In order to change the magnetic flux through the loop, what would you have to do?

9 Consider the situation shown. A triangular, aluminum loop is slowly moving to the right. Eventually, it will enter and pass through the uniform magnetic field region represented by the tails of arrows directed away from you. Initially, there is no current in the loop. When the loop is entering the magnetic field, what will be the direction of any induced current present in the loop? a) clockwise b) counterclockwise c) No current is induced.

10 Consider the situation shown. A triangular, aluminum loop is slowly moving to the right. Eventually, it will enter and pass through the uniform magnetic field region represented by the tails of arrows directed away from you. Initially, there is no current in the loop. When the loop is entering the magnetic field, what will be the direction of any induced current present in the loop? a) clockwise b) counterclockwise c) No current is induced.

11 Consider the situation shown. A triangular, aluminum loop is slowly moving to the right. Eventually, it will enter and pass through the uniform magnetic field region represented by the tails of arrows directed away from you. Initially, there is no current in the loop. When the loop is exiting the magnetic field, what will be the direction of any induced current present in the loop? a) clockwise b) counterclockwise c) No current is induced.

12 Consider the situation shown. A triangular, aluminum loop is slowly moving to the right. Eventually, it will enter and pass through the uniform magnetic field region represented by the tails of arrows directed away from you. Initially, there is no current in the loop. When the loop is exiting the magnetic field, what will be the direction of any induced current present in the loop? a) clockwise b) counterclockwise c) No current is induced.

13 A rigid, circular metal loop begins at rest in a uniform magnetic field directed away from you as shown. The loop is then pulled through the field toward the right, but does not exit the field. What is the direction of any induced current within the loop? a) clockwise b) counterclockwise c) No current is induced.

14 A rigid, circular metal loop begins at rest in a uniform magnetic field directed away from you as shown. The loop is then pulled through the field toward the right, but does not exit the field. What is the direction of any induced current within the loop? a) clockwise b) counterclockwise c) No current is induced.

15 A rectangular loop of wire is attached to a metal rod using rigid, electrically insulating rods so that the distance between the loop and metal rod is constant as the metal rod is rotated uniformly as shown. The metal rod carries a current in the direction indicated. Which of the following statements concerning an induced current in the rectangular loop as a result of the current in the metal rod is true? a) The induced current in the loop is clockwise around the loop. b) The induced current in the loop is counterclockwise around the loop. c) The induced current in the loop alternates between clockwise and counterclockwise around the loop. d) There is no induced current in the loop.

16 A rectangular loop of wire is attached to a metal rod using rigid, electrically insulating rods so that the distance between the loop and metal rod is constant as the metal rod is rotated uniformly as shown. The metal rod carries a current in the direction indicated. Which of the following statements concerning an induced current in the rectangular loop as a result of the current in the metal rod is true? a) The induced current in the loop is clockwise around the loop. b) The induced current in the loop is counterclockwise around the loop. c) The induced current in the loop alternates between clockwise and counterclockwise around the loop. d) There is no induced current in the loop.

17 1) clockwise 2) counterclockwise 3) no induced current If a coil is shrinking in a magnetic field pointing into the page, in what direction is the induced current? ConcepTest 23.4 Shrinking Wire Loop

18 decreasing into the page clockwise into the page The magnetic flux through the loop is decreasing, so the induced B field must try to reinforce it and therefore points in the same direction — into the page. According to the right-hand rule, an induced clockwise current will generate a magnetic field into the page. 1) clockwise 2) counterclockwise 3) no induced current If a coil is shrinking in a magnetic field pointing into the page, in what direction is the induced current? ConcepTest 23.4 Shrinking Wire Loop Follow-up: What if the B field is oriented at 90° to its present direction?

19 A wire loop is being pulled away from a current-carrying wire. What is the direction of the induced current in the loop? I 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.8a Loop and Wire I

20 into the page decreasing oppose this decrease into the page, clockwise The magnetic flux is into the page on the right side of the wire and decreasing due to the fact that the loop is being pulled away. By Lenz’s Law, the induced B field will oppose this decrease. Thus, the new B field points into the page, which requires an induced clockwise current to produce such a B field. I ConcepTest 23.8a Loop and Wire I 1) clockwise 2) counterclockwise 3) no induced current A wire loop is being pulled away from a current-carrying wire. What is the direction of the induced current in the loop?

21 What is the induced current if the wire loop moves in the direction of the yellow arrow ? 1) clockwise 2) counterclockwise 3) no induced current I ConcepTest 23.8b Loop and Wire II

22 magnetic flux through the loop is not changing no induced current The magnetic flux through the loop is not changing as it moves parallel to the wire. Therefore, there is no induced current. I 1) clockwise 2) counterclockwise 3) no induced current What is the induced current if the wire loop moves in the direction of the yellow arrow ? ConcepTest 23.8b Loop and Wire II

23 A conducting rod slides on a conducting track in a constant B field directed into the page. What is the direction of the induced current? x x x x x x x x x x x v 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.9 Motional EMF

24 A conducting rod slides on a conducting track in a constant B field directed into the page. What is the direction of the induced current? x x x x x x x x x x x v into the page increasing out of the page counterclockwise, The B field points into the page. The flux is increasing since the area is increasing. The induced B field opposes this change and therefore points out of the page. Thus, the induced current runs counterclockwise, according to the right-hand rule. 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.9 Motional EMF Follow-up: What direction is the magnetic force on the rod as it moves?

25 x x x x x x A wire loop is being pulled through a uniform magnetic field. What is the direction of the induced current? 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.3a Moving Wire Loop I

26 magnetic flux through the loop is not changingno current is induced Since the magnetic field is uniform, the magnetic flux through the loop is not changing. Thus no current is induced. x x x x x x A wire loop is being pulled through a uniform magnetic field. What is the direction of the induced current? 1) clockwise 2) counterclockwise 3) no induced current ConcepTest 23.3a Moving Wire Loop I Follow-up: What happens if the loop moves out of the page?

27 1) clockwise 2) counterclockwise 3) no induced current A wire loop is being pulled through a uniform magnetic field that suddenly ends. What is the direction of the induced current? x x x x x ConcepTest 23.3b Moving Wire Loop II

28 1) clockwise 2) counterclockwise 3) no induced current A wire loop is being pulled through a uniform magnetic field that suddenly ends. What is the direction of the induced current? B field into the page induced flux also into the page induced current in the clockwisedirection The B field into the page is disappearing in the loop, so it must be compensated by an induced flux also into the page. This can be accomplished by an induced current in the clockwise direction in the wire loop. x x x x x ConcepTest 23.3b Moving Wire Loop II Follow-up: What happens when the loop is completely out of the field?

29 1) clockwise 2) counterclockwise 3) no induced current What is the direction of the induced current if the B field suddenly increases while the loop is in the region? x x x x x x x x x x x ConcepTest 23.3c Moving Wire Loop III

30 1) clockwise 2) counterclockwise 3) no induced current What is the direction of the induced current if the B field suddenly increases while the loop is in the region? increasing B field into the page induced flux out of the page induced current in the counterclockwisedirection The increasing B field into the page must be countered by an induced flux out of the page. This can be accomplished by induced current in the counterclockwise direction in the wire loop. x x x x x x x x x x x ConcepTest 23.3c Moving Wire Loop III Follow-up: What if the loop stops moving while the field increases?


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