CBSE Class 11 » CBSE Class 11 Study Materials » Physics » Force and Magnetic Field

# Force and Magnetic Field

In this article, we will discuss magnetism, force and magnetic field, direction of force in magnetic field, force on charged particles in magnetic field and more.

The attraction or repulsion force produced by the motion of electrically charged particles is known as magnetic force. Due to this force, magnets are attracted or repelled to one another. Magnetic power can be found in a compass, a motor, the magnets that hold the refrigerator door shut, train lines, and modern roller coasters.

All moving charges generate a magnetic field, and charges passing through its areas experience a force.

## Magnetism

Iron objects are attracted to the poles of a bar magnet. The north pole is on one end, while the south pole is on the other. Magnetism is a phenomenon generated by the force exerted by magnets, which creates fields that attract or repel other magnetic objects. Electrically charged particles are the source of magnetism. The force which acts on electrically charged particles in a magnetic field is given by the magnitude of charge, the particle’s velocity, and the strength of the magnetic field.

## Force & Magnetic Field

### Magnetic Field

The magnetic field is the space or region around a magnet in which magnetic force is exerted on other magnets.

A magnetic compass helps to locate the magnetic field of a bar magnet. A magnetic compass does not deflect if it is maintained away from a magnet. When you bring a magnetic compass near a magnet, it deflects. If the magnetic field lines in a given place are very close to each other, the magnetic field is very strong, and if the magnetic field lines are very far apart, the magnetic field is very weak.

Magnetic field is represented in Tesla.

### Magnetic Force

The magnetic force is the attraction or repulsion force that originates from the motion of electrically charged particles. The magnetic force exerted on two moving charges by the magnetic field formed by the other can be represented as the force exerted on their charge by the magnetic field created by the other. The magnets are attracted or repellent to one another due to this force.

A compass, a motor, the magnets that hold food in the refrigerator, railroad tracks, and new roller coasters are all examples of magnetic force. A magnetic field is created by all moving charges, and the charges that move across its regions experience a force. Depending on whether the force is attractive or repulsive, it might be positive or negative. The magnetic force is determined by the object’s charge, velocity, and magnetic field.

### Direction of Magnetic Force

The direction of force in a magnetic field is represented by Fleming’s Left-Hand Rule and Fleming’s Right-Hand Rule.

#### Fleming’s Left-Hand Rule

Stretch out the forefinger, middle finger and thumb of your left-hand in such a way that they all are normal to one another. When the forefinger represents the direction of magnetic field, the middle finger represents the direction of current, then the thumb will represent the direction of the force in the magnetic field.

#### Fleming’s Right-Hand Rule

Stretch the forefinger, middle finger and the thumb of your right-hand in such a way that they all are normal to one another. When the forefinger represents the direction of magnetic field, the thumb represents the direction of motion of conductor, then the middle finger will represent the direction of induced emf (or current)

### Magnetic Lines of Force

Magnetic lines of force are curving lines that are used to depict a magnetic field. In fact, the number of lines corresponds to the strength of the magnetic field at a certain location. In addition, the tangent of any curve at a given position is parallel to the magnetic force at that location.

### Properties of Magnetic Lines of Force

1. Magnetic lines of force start from the North Pole and terminate at the South Pole.
2. Magnetic lines of force are continuous through the body of the magnet.
3. Magnetic lines of force can travel through iron more easily as compared to air.
4. Two magnetic lines of force never intersect one another.
5. Magnetic lines of force contract longitudinally.
6. Magnetic lines of force expand laterally.

### Force on Charged Particle in Magnetic Field

Force on charged particle in magnetic field is given as

F=BIl    ———— (1)

And, we know that

I=Q/t

Therefore, the of charged particle in magnetic field becomes

F=BI×Q/t   ———- (2)

And we also know that the velocity is given as

v=l/t

Therefore,

F=BQν   ——– (3)

Here,

F = magnetic force

B = magnetic field

I = current

Q = charge

l = length

t = time

v = velocity

### Conclusion

Magnetism is a phenomenon generated by the force exerted by magnets, which creates fields that attract or repel other magnetic objects.

Electrically charged particles are the source of magnetism.

The magnetic field is the space or region around a magnet in which magnetic force is exerted on other magnets.

A magnetic compass helps to locate the magnetic field of a bar magnet.

The direction of force in a magnetic field is represented by Fleming’s Left-Hand Rule and Fleming’s Right-Hand Rule.

Magnetic lines of force are curving lines that are used to depict a magnetic field.

Magnetic lines of force start from the North Pole and terminate at the South Pole.

Magnetic lines of force are continuous through the body of the magnet.

Force on charged particle in magnetic field is given as

F=BIl

Or

F=BI×Qt

Or

F=BQν

Get answers to the most common queries related to the CBSE 11th Examination Preparation.

## What is the source of the magnetic field of Earth?

Ans. The Earth’s magnetic field is formed deep within its nucleus. The movement of liquid iron at the Earth...Read full

## What is magnetic force?

Ans. The magnetic force is the attraction or repulsion force that originates from the motion of electrically charged...Read full

## What is Fleming's Left-Hand Rule?

Ans. Stretch out the forefinger, middle finger and thumb of your left-hand in such a way that they all are at normal...Read full