Sunday, September 11, 2016

Induced EMF due to Variable Current and Moving Conductor

When a circular coil placed above a current carrying conductor

Let us assume a circular coil above a current carrying conductor.Let us assume a case when a constant current is passing through the conductor. As constant current produce a constant magnetic field, there is no change in the field. Hence no induced EMF is generated in the closed coil.

Let us consider one more case where the conductor is carrying a increasing current. According to right hand thumb rule the direction of magnetic field around the current carrying conductor is outward. To oppose the generated magnetic field in the current carrying conductor, an inward magnetic field is generated in the coil nearby. Thus a clock wise current is generated in the closed coil.

Let us consider another case where the current in a straight conductor below the coil is decreasing. This generates a magnetic field inward and hence the magnetic field in the coil is outward. Thus the current in the coil is anticlockwise.

In another case let us assume an electron passing through a straight conductor. Thus the current in it is in the opposite direction. The magnetic field around it is in the clock wise direction. The induced emf in the closed coil to oppose it, anti clockwise current and north pole is generated on the face of the coil.

Motional EMF generated in a straight conductor when it is moved in a magnetic field with a certain velocity

We can move a current carrying conductor of known length with certain velocity in a magnetic field.

This rod will experience a force and we can measure it using the rule that we know all ready. We can also find the direction of the force experienced by the conductor using the Fleming left hand rule.

We can find the expression for the induced emf and current as shown in the diagram below.

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