Fields D.4 Electromagnetic Induction (id: 9385aabdd)

本题目来源于试卷: Fields D.4 Electromagnetic Induction，类别为 IB物理学

[单选题]
Two electric circuits with identical cells and resistances are on the same plane with the conductor loop as shown. Switch X is open and Switch Y is closed at the beginning and the center of the loop is at the same distance to the circuits.


Which of the following statement(s) is/are true about the induced current in the loop when changes to the switch positions are made?
I. When only switch X is closed the induced current will be in anti-clockwise direction.
II. When only switch Y is opened the induced current will be in clockwise direction.
III. When switch X is closed and switch Y is simultaneously opened there will be no induced current on the loop.

A. $I$ and $II$ only
B. $I$ and $III$ only
C. $II$ and $III$ only
D. $I$, $II$ and $III$


参考答案:  D


本题详细解析:
Explanation:

Current in both circuits cause a magnetic field on the loop, and they are in the same direction (into the page)

I. Correct
When switch X is closed there is an increase in the magnetic flux and according to Lenz's law, a current is induced in the loop in an anti-clockwise direction, so it opposes the increase in the flux.

II. Correct
When switch Y is opened, there will be a decrease in the magnetic flux, and according to Lenz' law, a current is induced on the loop in a clockwise direction, so it opposes the change in the flux.

III. Correct
When switch X is closed, and switch Y is opened, there will be a decrease and increase in the magnetic flux. Since everything is identical amount of increase and decrease will be equal, that is no change in magnetic flux. According to Faraday's law, no induced emf means no induced current.

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