# What is magnetic force – Troubleinthepeace

As was known in Chapter I, the quantity that characterizes the action of electric field to be Electric field strength. So which quantity will characterize the effect of magnetic ?

We invite you to follow the contentLesson 20: Magnetic force and magnetic induction to get the answer. Good luck with your studies!

1. Video lectures

2. Summary of theory

2.1. Magnetic force

2.2. Magnetic induction

3. Illustrated exercise

4. Practice lesson 20 Physics 11

4.1. Multiple-choice

5. Q&A Lesson 20 Chapter 4 Physics 11

2.1.1. Even magnetic field A uniform magnetic field is a magnetic field whose properties are the same at all points; Magnetic lines of force are parallel lines, in the same direction, and equally spaced.

You are watching: What is Magnetic Force?

A uniform magnetic field can be created between the two poles of a U-shaped magnet.

2.1.2. Magnetic force due to a uniform magnetic field acting on a current-carrying conductor The magnetic force acting on a piece of current-carrying conductor placed in a uniform magnetic field is perpendicular to the magnetic lines of force and perpendicular to the conductor, whose magnitude depends on the magnetic field and the magnitude of the current flowing through the wire. guide

### 2.2. Inductive

2.2.1. Inductive

Magnetic induction at a point in a magnetic field is a quantity that characterizes the strength and weakness of the magnetic field and is measured as the quotient between the magnetic force acting on a current-carrying conductor perpendicular to the magnetic induction line at the point. and the product of the amperage and the length of that conductor.

(B = fracFIl)

2.2.2. Magnetic induction unit

In the SI system, the unit of magnetic induction is the tesla (T).

(1T = frac1N1A.1m)

2.2.3. Magnetic induction vector

Magnetic induction vector ( match Blimits^ to ) at a point:

There is a direction that coincides with the direction of the magnetic field at that point.

Has magnitude: (B = fracFIl)

2.2.4. General expression of magnetic force

Magnetic force (mathop Flimits^ to ) acting on a current element (Imathop llimits^ to ) placed in a uniform magnetic field, where there is a magnetic induction (mathop Blimits^ to ):

There is a point located at the midpoint of l;

There are directions perpendicular to (mathop llimits^ to ) and (mathop Blimits^ to ) ;

There is a direction that follows the left hand rule

Has magnitude (F = IlBsinalpha ) ## Illustrated exercise

Lesson 1:

Compare electric force and electromagnetic force.

Solution guide:

Electric force is the force exerted by an electric field on a charge placed in it, and magnetic force is the force due to a magnetic field acting on a magnet or an electric current placed in it.

Expression:

Electric force (F = qE) (where q is the charge and E is the electric field strength).

Magnetic force: (F = IlBsinalpha ) (where (alpha ) is the angle formed by and , (I) is the amperage, (l) is the length of the conductor and B is the magnitude of the magnetic induction).

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Lesson 2:

The current element (Ioverrightarrow l ) is suspended horizontally in a uniform magnetic field. What must be the direction and magnitude of the magnetic induction B so that the electromagnetic force is balanced with the gravity (mg) of the current element?

Solution guide:

In order for the electromagnetic force to balance with the gravity (mg) of the magnetic part of the current, the direction of the magnetic induction B must be horizontal, then the magnetic force acting on the wire segment is directed upwards.

The magnitude of magnetic induction B is: (f = IlBsinalpha rm = mg)

Lesson 3:

Which statement below is incorrect?

Electromagnetic force acting on a current element:

A. perpendicular to the current element

B. same direction as the magnetic field

C. proportional to the amperage

D. proportional to magnetic induction.

Solution guide:

The magnetic force acting on a piece of current-carrying wire placed in a uniform magnetic field is perpendicular to the magnetic lines of force and perpendicular to the conductor, whose magnitude depends on the magnetic field and the magnitude of the current flowing through the wire. guide

Lesson 4:

Which of the following statements is correct?

Magnetic induction at a point in the magnetic field:

A. perpendicular to the magnetic field lines.

B. lies in the direction of the magnetic field lines.

C. lies in the direction of the electromagnetic force.

D. has no definite direction.

Solution guide

Magnetic induction at a point in the magnetic field in the direction of the magnetic field line.

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