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# Magnetic Fields

Magnets have bewildered everyone from the Insane Clown Posse to Tim Allen. Stand apart from the madding crowd and set yourself straight on the fields of moving charges.

# Ampere's law (qualitative)

A current of $$i$$ flows through a straight wire $$a,$$ and a current of $$2i$$ flows through another straight wire $$b$$ which is $$2d$$ away from $$a ,$$ as shown in the above figure. Which of the following is an appropriate comparison of the magnitudes of the magnetic field strengths at the three points $$A, B$$ and $$C?$$

A solenoid has current flow $$I ,$$ as shown in the above figure. What is the direction of the magnetic field at point $$A?$$

Current $$i$$ flows through a straight wire, as shown in the above figure. Which of the following is an appropriate comparison of the magnitudes of the magnetic field strengths?

A toroid has current flow $$I,$$ as shown in the above figure. What is the direction of the magnetic field at point $$A?$$

A solenoid has current flow $$i ,$$ as shown in the above figure. Which of the following is an appropriate comparison of the magnitudes of the magnetic field strengths at the three points $$A, B$$ and $$C?$$

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