Now the switch on the electromagnet is reopened. The magnitude of the external magnetic flux through the wire loop (A. increases, B. decreases, C. remains constant), and there is _ (A. zero, B. a clockwise, C. a counterclockwise) current induced in the loop (as seen from the left. Enter the letters corresponding to the responses that correctly complete the statement above. For example: A,C View Available Hint(s)

Oersted had shown that an electric current creates a magnetic field around him. Many scientists tried to obtain the inverse phenomenon, induce an electric current from a magnetic field.

We can explain that the magnitude of the magnetic flux through the spiral decreases and is transported clockwise thanks to Faraday's experiences for the explanation of electromagnetic induction.

Experiences of Faraday (1831)

1st Experience

Two coils are wrapped around an iron bar. The first is connected to a powerful battery, the second to a galvanometer to measure the induced current when closing and opening the switch.

Results:

When the switch is switched on, an electric current is induced in the second coil. The currents in the two coils circulate in opposite directions.

When the switch is turned off, an electric current is induced again in the second coil. Now the induced current makes sense opposite to the previous case.

Faraday concludes that current is induced in the second coil while increasing or decreasing the current intensity in the first coil, not while remaining constant. The induction of electric current in a circuit is due to variable magnetic fields.

2nd Experience

We connect a coil to a galvanometer to be able to measure the induced current when introducing and removing a magnet.

Results:

If we bring the magnet closer to the coil, an induced current appears during the movement of the magnet. The direction of the induced current in the coil is reversed if we move the magnet away. With the fixed coil and magnet there is no induced current.