[Physics Class Notes] on Difference Between Electric Field and Magnetic Field Pdf for Exam

In this article, you will find the proper explanation of what an electric field and a magnetic field are. The differences have been pointed out in simpler language for a better understanding of the students. Check the explanation and develop your conceptual foundation in this topic exceptionally. 

What is the Electric Field?

Electric field or electric field intensity is the force surrounding an electrically charged particle. We can also say that it is the area where the line of force exists and these lines of force surround the electric field. These lines of force are imaginary lines that are used to define the area of influence around the electric charge. It is a vector quantity as it has both direction and magnitude. The symbol used to express the electric field is the letter E. It’s unit of measurements is Newton/Coulomb.

 

What is the Magnetic Field?

The area around the magnet where attractive forces or repulsive forces are exhibited by the poles of the magnet is called magnetic field.  When electric charges move across space or an electrical conductor, a magnetic field is induced due to its motion.

 

Comparing the Two Fields

1. Unit 

The unit for Electric field is Volt/meter or Newton/coulomb. 

 

Whereas, the unit for Magnetic field is: Tesla, (Newton × Second)/(Coulomb × Meter) 

 

2. Denotation

The electric field is denoted by E

 

The magnetic field is denoted by B

 

3. Formula

The formula of Electric Field, = Newton/ Coulomb (N/C)

 

Whereas, the formula of Magnetic field, = Tesla or wb/m²

 

4. Measuring Instrument

An electrometer is used to measure the electric field whereas the magnetometer is used to measure the Magnetic field.

 

5. Pole

In an electric field, monopoles (single charges) exist. In an electric field single positive and negative charges exist. For monopoles, like positrons and electrons, there are straight field lines either towards or away from the charge.

 

In a magnetic field, only dipoles exist. Monopoles do not exist. This is because magnetic field lines start from the north pole and end at the south pole. Therefore, magnetic fields have both poles i.e. dipoles only. 

 

6. Electric field and magnetic field are perpendicular to each other. The electric field is perpendicular to the magnetic field and vice-versa.

7. Field lines are imaginary lines that define the area where the force or influence of the charge is effective. This charge can be an electric charge or a magnetic dipole.

For an electric charge, the field lines are straight. For a position, they are outwards and for an electron, they are inwards.

For a magnetic dipole, they start at the north pole and terminate on the south pole.

8. The field is the area of influence around any charge or magnet. Both electric and magnetic fields are vectors. They have directions and magnitude.

9. The electric field is defined by straight field lines. They do not form closed loops.

Magnetic field lines form a closed loop starting from the north pole and terminating at the south pole outside the magnet. 

10. There are two types of charges present in an electric field. The positive charge is called the positron and the negative charge is called the electron.

11. The force between the charges is the same. Like repels like. A positron repels a positron but attracts an electron. Same way, the north pole repels the north pole but attracts the south pole.

12. Dimensionally, an electric field exists in two dimensions whereas magnetic fields exist in three dimensions.

13. Work is done by the field when a particle enters its field of influence.

The electric field can do work. When a particle enters an electric field, the electric field can influence the particle by changing its velocity as well as its direction.

The magnetic field cannot do any work. When any particle enters the area of influence of a magnet, the magnet field cannot affect the velocity or direction of this particle. Basically, the work done by a magnetic field on a particle is zero.

 

Brief About the Discovery of the Electron and its Ramifications

The finding of the electron in 1898 brought up a whole new field of study: the nature of the electric charge and of matter itself. The finding of the electrons came out of the research of electric flows in vacuum tubes. Heinrich Geissler, a glassblower who aided the German physicist Julius Plücker, developed the vacuum tube in 1854. From then till the end of the century, the characteristics of cathode-ray discharges were investigated thoroughly. 

 

Crookes believed that the rays were composed of electrically charged particles. In 1898 another English physicist, Sir J.J. Thomson defined a cathode ray as a stream of negatively charged particles. Each of these were having a mass of 1/1836 less than that of a hydrogen ion. Thomson’s finding confirmed the particulate nature of the charge; his particles were eventually termed electrons.