Test: Electricity - 3 - UPSC MCQ

The electric field is the region around a charged particle where the lines of force can be felt by another charge by getting repulsed or attracted as per their sign of charges.

Electric Field Intensity (E): The electrostatic force acting per unit positive charge on a point in an electric field is called electric field intensity at that point.

Electric potential: An electric potential is defined as the amount of electric potential energy that a unitary point electric charge would have if located at any point of space.
It is equal to the work done by an electric field in carrying a unit positive charge from infinity to that point.

Potential difference is the difference in electric potential energy between two points.
It is the amount of work done in moving a unit positive charge from one point to another point in an electric field. This is measured in volt. 

Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge.

Electricity constituted by moving electric charge is called current.

Current is defined as the amount of electric charge flowing through a cross-section of circuits in unit time.
I = Q/T

As we know the current is the flow of charges so it requires a potential difference between the two points.

Cell is the device which is used to maintain the potential difference between two points of the conductor.

An electric circuit is the representation of the whole path of current and also the various devices connected in it, like Cell, Resistor, etc.

A voltmeter is an instrument used for measuring the electrical potential difference between two points in an electric circuit.

Ammeter is used to measure electric current because it has very low resistance and are always connected in series

An electric current is said to exist when there is a net flow of electric charge through a region. In electric circuits this charge is often carried by electrons moving through a wire.

Conventional current or simply current, behaves as if positive charge carriers cause current to flow. Conventional current flows from the positive terminal to the negative.

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points.

As the temperature of a metallic conductor increases, the kinetic energy of the electrons of the conductor also increases
Due to this increase in kinetic energy more obstruction is offered to the flowing electrons i.e. current.
Therefore, as more obstruction is offered to the flowing electrons, the resistance is increased.

When two or more resistors are connected in series, the total resistance of the combination is equal to the sum of all the individual resistances.

Thus, the total resistance of the circuit will always increase.

To find the total resistance of all components, the reciprocals of the resistances of each component are added and the reciprocal of the sum is taken. 

Thus, the Total resistance will always be less than the value of the smallest resistance.

where,
R = resistance,
ρ = resistivity,
ℓ = length,
A = area of cross-section

From the above relation: R ∝ ℓ
⇒ resistance increases due to an increase in length 
Because the electrons have suffered greater collisions with atoms in the material.

In parallel combination, change in length will not be effective, therefore we consider the area of cross-section.
As we know that resistance is inversely proportional to the area of cross-section.

Thus, resistance will decrease with an increase in area of crosssection.

Since electrons are negative they should be repelled by the negative charge and attracted by the positive charge, i.e., in an electric field the electrons must move from regions of low potential to the regions with high potential by the action of the electrical forces.

Electrical resistivity of a given metallic wire depends on number density of free electrons in the conductor which is the nature of material

A positively charged subatomic particle that is housed within the nucleus is caled Proton.

A negatively charged subatomic particle that has negligible mass and moves around in a cloud around the nucleus is called Electron.

Materials with high electron mobility (many free electrons) are called conductors, while materials with low electron mobility (few or no free electrons) are called insulators.