**The magnitude of the current in the 20 ω resistor is 0.6 A, and the direction is from left to right.**

What are the magnitude and direction of the current in 20 ω resistors? As we have seen, a changing magnetic field will induce an electric field. This is the basis for many electrical devices such as generators and motors. The strength of the induced electric field depends on the rate of change of the magnetic field. If the magnetic field changes quickly, a strong electric field will be induced. If the magnetic field changes slowly, a weaker electric field will be induced.

We can quantitatively describe this relationship between the magnetic field and the induced electric field using Faraday’s law of induction. This states that the magnitude of the induced electric field is proportional to the rate of change of the magnetic flux through a given area. The SI unit for magnetic flux is the weber (Wb), and the unit for the induced electric field is the volt per meter (V/m).

The magnetic flux through an area is given by:

where B is the magnitude of the magnetic field, A is the surface area, and θ is the angle between the magnetic field and the normal to the surface. The SI unit for magnetic flux is the weber (Wb).

Faraday’s law of induction states that:

where E is the magnitude of the induced electric field, ΔΦB/Δt is the rate of change of magnetic flux, and t is time. The SI unit for the induced electric field is volts per meter (V/m).

We can see from Faraday’s law that the induced electric field will be strongest when the magnetic flux changes quickly. This is because the rate of change of magnetic flux is proportional to the induced electric field.

We can also see that the direction of the induced electric field will be such that it will oppose the change in magnetic flux. This is known as Lenz’s law.

Lenz’s law states that:

The induced electric field will always oppose the change in magnetic flux that caused it. In other words, if we start with a changing magnetic flux, then the induced electric field will try to stop this change.

This has important implications for electrical devices such as generators and motors. We will discuss this in more detail in the next section.