Electrostatic Charges

ELECTRIC CHARGE

 Electric Charge is the property of subatomic particles that causes it to experience a force when placed in an electric and magnetic field.”
Electric charges are of two types: Positive and Negative, commonly carried by charge carriers protons and electrons.
Examples of the types of charges are subatomic particles or the particles of matter:

  • Protons are positively charged.
  • Electrons are negatively charged.
  • Neutrons have zero charge.

Electric charge is a scalar quantity. Apart from having a magnitude and direction, a quantity to be termed a vector should also obey the laws of vector addition, such as triangle law of vector addition and parallelogram law of vector addition; only then the quantity is said to be a vector quantity. When two currents meet at a junction, in the case of an electric current, the resultant current of these will be an algebraic sum and not the vector sum. Therefore, an electric current is a scalar quantity, although it possesses magnitude and direction.

Measuring Electric charge

Coulomb is the unit of electric charge.

“One coulomb is the quantity of charge transferred in one second.”

Mathematically, the definition of a coulomb is represented as:

Q = I.t

In the equation, Q is the electric charge, I is the electric current and t is the time.

Overview of Electric Charge

Definition

Electric Charge is the property of subatomic particles that causes it to experience a force when placed in an electromagnetic field.

Symbol

Q

Formula

Q = I.t

SI Unit

Coulomb

Other Units

Faraday, Ampere-Hour

Properties of Electric Charge

Various properties of charge include the following:

  • Additivity of Electric Charge
  • Conservation of Electric Charge
  • Quantization of Electric Charge

In an isolated system, Electric charge is conserved, which means the net electric charge of the system is constant. The algebraic sum of the fundamental charges in any isolated system remains the same.

Additivity of Electric Charge

Let us consider a system of charges containing three point charges with magnitudes q1, q2, and q3. In such a system, the total charge of the system can be obtained by algebraically adding the three charges.

These charges have magnitude but no direction, are scalar quantities, and are treated as real numbers during any operation. For a system containing n particles, the total charge of the system can be written as

We note that the charge can either be positive or negative and the operation takes the sign of the charge into consideration.

Conservation of Electric Charge

According to the principle of conservation of conservation of charges, charges are not created or destroyed; they simply move from one body to another. For example, when two objects, one charged and one uncharged, come into contact, the charge will move from one charged object to the uncharged object until the charge is evenly distributed in the whole system. Here the charge is neither created nor lost, but simply transferred from an excess supply to another with a deficit.

Quantization of Electric Charge

According to the principle of quantization of electric charge, all the free charges are integral multiples of a basic predefined unit, which we denote by e. Thus, the charge possessed by a system can be given as,

Where n is an integer (zero, a positive or a negative number) and e is the basic unit of charge, that is, the charge carried by an electron or a proton. The value of e is 1.6 × 10-19C.

Types of Electric Charge

Two kinds of electric charges are there

  • positive(+) charge
  • negative(-) charge

Negative Charge

When an object has a negative charge it means that it has more electrons than protons.

Positive Charge

When an object has a positive charge it means that it has more protons than electrons.

When there is an identical number of positive and negative charges, the negative and positive charges would cancel out each other and the object would become neutral.

Methods of Charging

The process of supplying the electric charge to an object or losing the electric charge from an object is called charging.

An uncharged object can be charged in three different ways as follows:

  • Charging by friction ( triboelectric charging)
  • Charging by conduction
  • Charging by induction

Charging by Friction

When two objects rub against each other, a charge transfer occurs. One object loses electrons while the other object gains electrons. An object that loses electrons becomes positively charged and an object that gains electrons becomes negatively charged. Both objects are charged by friction and this method of charging is generally known as frictional electrification.

Charging by Conduction

The method of charging an uncharged object by bringing it close to a charged object is known as charging by conduction. The charged conductor has an unequal number of protons and electrons; hence when an uncharged conductor is brought near it, it discharges electrons to stabilise itself.

Charging by Induction

The process of charging an uncharged conductor by bringing it near a charged conductor without any physical contact is known as charging by induction.