Chapter 21 Review Questions

# That the loop is being pulled away by lenzs law the

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Unformatted text preview: ase. Thus, the new oppose B field points into the page, which into requires an induced clockwise current to clockwise produce such a B field. 1) clockwise 2) counterclockwise 3) no induced current I ConcepTest 21.8b Loop and Wire II ConcepTest Loop What is the induced current if 1) clockwise the wire loop moves in the 2) counterclockwise direction of the yellow arrow ? 3) no induced current I ConcepTest 21.8b Loop and Wire II ConcepTest Loop What is the induced current if What 1) clockwise the wire loop moves in the 2) counterclockwise direction of the yellow arrow ? 3) no induced current The magnetic flux through the loop is not changing as it moves parallel is to the wire. Therefore, there is no induced current. induced I ConcepTest 21.9 Motional EMF ConcepTest Motional A conducting rod slides on a conducting track in a constant 1) clockwise B field directed into the page. 2) counterclockwise What is the direction of the 3) no induced current induced current? xxxxxxxxxxx xxxxxxxxxxx xxxxxxxxxxx xxxxxxxxxxx v ConcepTest 21.9 Motional EMF ConcepTest Motional A conducting rod slides on a conducting track in a constant 1) clockwise B field directed into the page. 2) counterclockwise What is the direction of the 3) no induced current induced current? The B field points into the page. into The flux is increasing since the increasing area is increasing. The induced B field opposes this change and therefore points out of the page. out Thus, the induced current runs counterclockwise according to counterclockwise the right-hand rule. xxxxxxxxxxx xxxxxxxxxxx xxxxxxxxxxx v xxxxxxxxxxx Follow-up: What direction is the magnetic force on the rod as it moves? ConcepTest 21.12a Transformers I ConcepTest Transformers 1) 30 V 1) What is the voltage What 2) 60 V across the lightbulb? 3) 120 V 4) 240 V 5) 480 V 120 V 120 ConcepTest 21.12a Transformers I ConcepTest Transformers 1) 30 V 1) What is the voltage What 2) 60 V across the lightbulb? 3) 120 V 4) 240 V 5) 480 V The first transformer has a 2:1 ratio first 2:1 of turns, so the voltage doubles. voltage But the second transformer has a second 1:2 ratio, so the voltage is halved 1:2 voltage again. Therefore, the end result is the same as the original voltage. same 120 V 240 V 120 V ConcepTest 21.12b Transformers II Transformers 1) 1/4 A 1) Given that the intermediate Given 2) 1/2 A current is 1 A, what is the 3) 1 A current through the 4) 2 A lightbulb? 5) 5 A 1A 120 V 240 V 120 V ConcepTest 21.12b Transformers II Transformers 1) 1/4 A Given that the intermediate Given 2) 1/2 A current is 1 A, what is the 3) 1 A current through the 4) 2 A lightbulb? 5) 5 A Power in = Power out Power 240 V × 1 A = 120 V × ??? 1A The unknown current is 2 A. The 120 V 240 V 120 V ConcepTest 21.12c Transformers III ConcepTest Transformers A 6 V battery is connected to one side of a transformer. Compared to the voltage drop across coil A, the voltage 2) 6 V 3) less than 6 V 4) zero across coil B is: A 6V 1) greater than 6 V 1) B ConcepTest 21.12c Transformers III ConcepTest Transformers A 6 V battery is connected to 1) greater than 6 V one side of a transformer. 2) 6 V Compared to the voltage drop 3) less than 6 V across coil A, the voltage 4) zero across coil B is: The voltage across B is zero. The Only a changing magnetic flux changing induces an EMF. Batteries can only provide DC current. DC A 6V B...
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## This document was uploaded on 09/24/2013.

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