Electric Field Unit

In order to measure any physical quantities and for the measurement to make sense, it is necessary that we attach a unit along with the number. A unit is a standard of measurement which has a clear definition and helps attach significance to a number.

All physical quantities must compulsorily have a unit associated with them. The electric field is also a physical quantity with Newton/Coulomb as its unit. This electric field unit is derived from the formula of the electric field. Newton/Coulomb is the S.I. unit of the electric field. Let’s study in-depth about this.

The Electric Field

It is a universal law that states that any electrically charged particle situated anywhere in space will form an electric field surrounding it. The charges can move in relation to each other based on whether they attract or repulse each other. Hence, the charge which is forming the electric field will exert some force on the other charged particle which enters its force field.

This force helps in the calculation of the strength of the electric field or force field which the original charged particle exerts. Since it also has a direction, the electric field or the electric field strength can be regarded as a vector quantity.

The Electric Field Units

The units which are associated in measurements of a physical quantity depend upon which fundamental physical quantities the derived quantities depend on. 

For example, the unit of speed will depend upon the unit of distance and time as they constitute the formula for speed. The unit of distance is metre and the unit of time is second. Hence, the unit of speed will be m/s.

A similar concept is applied while calculating the unit for electric field intensity or the electric field.

Deriving the Units for Electric Field

In order to derive the units for the electric field, we need to see how it is measured and the formula used to do the same.

The electric field is measured with the help of electric field intensity. Electric field intensity is the charge experienced by a unit test charge placed in the electric field of a source charge.

The formula for electric field intensity is:

Electric field intensity = force/Charge

Here, the force is the pull or push experienced by the test charge and the charge is the original positive or negative charge of the test charge.

Now the force is generally measured in Newtons. The standard unit for the charge is Coulombs. So, the unit of the electric field will be a combination of both these units. However, the force is divided by the charge. Hence the following conditions will be true.

The electric field intensity will be directly proportional to the force exerted on the charged particle. The electric field intensity will be inversely proportional to the original charge of the test charge particle.

The same conditions will be applied to the units. The unit of force will be directly proportional with the electric field unit, and the unit of charge will be inversely proportional.

Hence, the unit of electric field intensity is Newton / Coulomb.

Each physical quantity generally has two types of units associated with it. Let’s take a look at those for the electric field. The Volts per Metre is the standard or the S.I. unit of the electric field. The C.G.S unit of electric field intensity is N/C or the Newton/Coulomb.

Dimensions of Electric Field Unit

Each unit is associated with certain dimensions. These dimensions help us identify what basic units have constituted the derived units and help us compare the units with each other. The dimensions of the unit can be derived from the formula of the physical quantities.

For the electric field intensity, its formula is Force/charge. The force is a product of mass into acceleration. Hence, the dimensional formula for force will be MLT-2. The electric charge flow is measured by multiplying the charges into time per second.

Hence, the dimensional formula for the charge is T-I.

To calculate the dimensional equation for the electric field unit, we combine their two formulas.

The dimensional formula for the electric field strength unit will be:

MLT-2 / TI

which is equal to MLT-3I-1

This tells how that electric field unit is related to the fundamental units.

The dimensional equation is MLT-3I-1 which means the electric field unit is directly proportional to the following fundamental units.

• Mass
• Length

The electric field unit is inversely proportional to the following fundamental units.

• Time
• Current

Such is the concept of the electric field, the electric field unit and the S.I. unit of the electric field. However, the C.G.S unit of the electric field, that is, Newton/Coulombs, is more commonly preferred.

Conclusion

A unit is required to attach a meaning to any number which measures physical quantity. The strength of the electric field is the charge experienced by the discharge placed in the electric field. The unit used to measure the electric field intensity is Newtons/Coulomb. The C.G.S. unit is Volts per metre.

This unit is derived from the formula for electric field intensity, which is equal to

E = Force/Charge

Here the force is the force exerted on the test charge by the electric field and the charges the original charge of the test charge.