# Magnetic Fields & Forces on Conductors

• Jimmy87
In summary, the problem asks for the force on a 1 cm section of the loop, not a 1 cm section of the wire. The resultant force on a section of the LOOP is zero, meaning that ☹️.
Jimmy87
Homework Statement
Multiple Choice Question
Relevant Equations
F = BIL sin (θ)
Hi,

Here is a multiple choice question I am stuck with and would appreciate some guidance:
The mark scheme for this paper says it is option A - 0N. I didn't get that at all. If a current carrying wire is in a magnetic field with some component perpendicular to the field then how can it be zero?! I got option B by doing

F = BIL sin (θ) where θ is the angle between B and I.
F = (0.08T x 0.5A x 0.01m) sin (30) = 2.0 x 10-4 N (to 2 sig figs)

Have I missed something?

Thanks.

The wording of the problem is not particularly clear. It asks for the force on a section of the loop, not the force on a section of the wire. A section of the loop might be interpreted as containing two sections of the wire.

Jimmy87
In my opinion this is almost deceptively tricky. However note that they said “1cm section of the loop”, not “1cm section of the wire”. I believe they mean you to understand that a “section of the loop” includes both wires. While there is indeed a force on the outgoing and returning wires, the forces on each are in opposite directions. The net force is zero. There would be a torque on the loop, but the wires are close together making the lever arm small, so the torque is also small.

Jimmy87
Cutter Ketch said:
In my opinion this is almost deceptively tricky. However note that they said “1cm section of the loop”, not “1cm section of the wire”. I believe they mean you to understand that a “section of the loop” includes both wires. While there is indeed a force on the outgoing and returning wires, the forces on each are in opposite directions. The net force is zero. There would be a torque on the loop, but the wires are close together making the lever arm small, so the torque is also small.

Thanks. Wow that’s crazy! I see what you mean now. The resultant force on a section of the LOOP is zero. That’s mean . They should have at least but loop in bold font.

Thanks guys.

## 1. What is a magnetic field and how is it created?

A magnetic field is a region of space where a magnetic force can act on a magnetic material. It is created by moving electric charges, such as electrons, which generate a magnetic field around them. This can be seen in the flow of electricity through a wire, where the electric current creates a magnetic field around the wire.

## 2. How do magnetic fields interact with conductors?

Magnetic fields can induce an electric current in a conductor, also known as electromagnetic induction. This occurs when a conductor is moved within a magnetic field or when the strength of the magnetic field changes. The electric current created in the conductor will then produce its own magnetic field, which can interact with the original magnetic field.

## 3. What is the difference between a magnetic field and an electric field?

A magnetic field is created by moving electric charges, while an electric field is created by stationary electric charges. Additionally, magnetic fields act on magnetic materials and can induce electric currents, while electric fields act on charged particles and can cause them to move.

## 4. How does the strength of a magnetic field affect conductors?

The strength of a magnetic field can affect conductors in several ways. A stronger magnetic field can induce a larger electric current in a conductor, and it can also cause a greater force on a conductor that is moving within the field. Additionally, the direction of the magnetic field can determine the direction of the induced current in the conductor.

## 5. How are magnetic fields and forces used in everyday life?

Magnetic fields and forces are used in various everyday applications, such as generators, motors, and speakers. They are also used in medical imaging technologies like MRI machines and in transportation systems like maglev trains. Additionally, magnetic fields are used in compasses for navigation and in credit cards for data storage.

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