Coils P and Q each have a large number of turns of insulated wire. When switch S is closed, the pointer of galvanometer G is deflected toward the left. With S now closed, to make the pointer of G deflect toward the right one could:
Correct answer: B. Open S
- A. Move coil P toward coil Q
- B. Open S
- C. Move coil Q toward coil P
- D. Move the slide of the rheostat R quickly to the right
Explanation
Closing the switch causes an increasing magnetic flux in Q, inducing a current (left deflection). To get an opposite deflection (right), we need a decreasing magnetic flux. Opening the switch will cause the current in P to drop to zero, creating a decreasing flux in Q and inducing a current in the opposite direction.
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About Electromagnetism
Magnetic flux density and magnetic flux describe the strength of a magnetic field and the field passing through a surface. A charged particle moving through a magnetic field experiences a force perpendicular to its velocity and may follow circular or helical motion, depending on the angle between velocity and field.
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