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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 righthand rule. xxxxxxxxxxx
xxxxxxxxxxx
xxxxxxxxxxx v xxxxxxxxxxx Followup: 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.
 Spring '13

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