# What is the Magnetic Flux through a Loop with Opposite Magnetic Fields?

• ATT182
In summary, the magnetic fields in the loop are going in opposite directions, so the flux through the loop is negative.
ATT182

## Homework Equations

Flux = DeltaB * Area

## The Attempt at a Solution

: Since the magnetic fields are going in opposite directions through the loop, I assumed that they would have different signs, so I chose 2.0 T to be positive and 1.0 to be negative, so when calculating the change in magnetic field, I did -1.0-2.0 = -3.0. Why is this not the case? Thanks![/B]

Last edited:
Welcome to PF!

ATT182 said:
so when calculating the change in magnetic field, I did -1.0-2.0 = -3.0. Why is this not the case? Thanks!

You are not asked to find a change in flux. You just need to find the total flux through the entire loop.

Imagine dividing the loop into left and right halves.

The change in field with respect to spatial variable is indeed -3 as we move from right to left, BUT

Faraday's law wants us to calculate the change in flux with respect to the time variable.

TSny said:
Welcome to PF!
You are not asked to find a change in flux. You just need to find the total flux through the entire loop.

Imagine dividing the loop into left and right halves.
Thank you! I'm starting to see it, but isn't the flux due to a change in magnetic field? So I'm still not so sure why you wouldn't choose one to be negative. Is this because flux is a scalar quantity?

ATT182 said:
isn't the flux due to a change in magnetic field?
Flux is essentially just the number of magnetic field lines piercing through the loop. Field lines in one direction count positive while field lines in the opposite direction count negative.

If the magnetic field changes, or if the size of the loop changes, or if the orientation of the loop changes, then the flux through the loop can change. A change in flux induces an emf in the loop.

But this problem is not concerned with emf or with a change in flux. It just asks for the flux for the situation shown in the figure.

ATT182

## 1. What is magnetic flux through a loop?

Magnetic flux through a loop refers to the measure of the strength and direction of a magnetic field passing through a closed loop or surface. It is given by the product of the magnetic field and the area of the loop or surface.

## 2. How is magnetic flux through a loop calculated?

Magnetic flux through a loop is calculated by multiplying the strength of the magnetic field passing through the loop by the area of the loop in a direction perpendicular to the magnetic field.

## 3. What is the unit of measurement for magnetic flux through a loop?

The unit of measurement for magnetic flux through a loop is Weber (Wb) or Tesla-meter squared (Tm²).

## 4. How does the orientation of the loop affect the magnetic flux passing through it?

The orientation of the loop has a significant impact on the magnetic flux passing through it. If the loop is parallel to the magnetic field, the flux will be maximum. On the other hand, if the loop is perpendicular to the field, the flux will be zero.

## 5. What is the significance of magnetic flux through a loop?

Magnetic flux through a loop has several applications in various fields such as electromagnetism, power generation, and magnetic storage devices. It helps in understanding the behavior of magnetic fields and their effects on electric currents.

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