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SAT® Subject Test in Physics

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Difficult

Turning Current On and Off

SATPHY-KSXVJK

The picture below shows a wire carrying conventional current toward the west (when the current is turned on). The wire is positioned directly north of a flat rectangular horizontal loop of wire with a resistor located on the south side of the loop.

The picture shows the whole arrangement as viewed from above. At the start, let's assume that NO current flows in the red wire.

Consider the direction of current induced through the resistor during three events:

1) The current is suddenly turned on.

2) The current remains on at a constant value.

3) The current is suddenly turned off.

Which of the following tables is correct?

A
Direction of Current through Resistor when Current Suddenly Turned On west
Direction of Current through Resistor when Current Remains Constant no current
Direction of Current through Resistor when Current Suddenly Turned Off west
B
Direction of Current through Resistor when Current Suddenly Turned On east
Direction of Current through Resistor when Current Remains Constant west
Direction of Current through Resistor when Current Suddenly Turned Off east
C
Direction of Current through Resistor when Current Suddenly Turned On east
Direction of Current through Resistor when Current Remains Constant no current
Direction of Current through Resistor when Current Suddenly Turned Off west
D
Direction of Current through Resistor when Current Suddenly Turned On west
Direction of Current through Resistor when Current Remains Constant no current
Direction of Current through Resistor when Current Suddenly Turned Off east
E
Direction of Current through Resistor when Current Suddenly Turned On west
Direction of Current through Resistor when Current Remains Constant east
Direction of Current through Resistor when Current Suddenly Turned Off west