Question

Define:

(1) 1 volt PD

(2) 1 ampere

(3) 1 ohm

(4) Potential

(5) Resistivity

(6) Electric power

Answer 1

(1) 1 volt PD: If one joule of work is required to move 1 coulomb of electric charge from one point to another, it is said that potential difference between two points is 1 volt.

PD = Work done /charge

1 V = 1J/1C

(2) 1 ampere: Ampere (A) is the SI unit of current. So when 1 coulomb of charge flows through a wire for 1second, the current through the wire is said to be 1 Ampere.

Current = charge / time.

1 A = 1C/1s

(3) 1 ohm: When a potential difference of 1V across a wire gives rise to 1A current through the wire, the resistance of the wire is said to be 1 Ω.

1Ω = 1V/1A

(4) Potential: Potential or Electric potential is defined as the work done in bringing a unit positive charge slowly (acceleration = 0) from infinity to a given point at a certain distance against the electric field of a charge.

The electric potential is given by,

(5) Resistivity: Resistivity is the characteristic property of a material which depends on the nature of the material and not its dimensions. It is the measure of a material’s ability to oppose the flow of current. SI unit of resistivity is Ohm meter, Ω m. Resistivity of the material changes with temperature.

Following is the equation relating resistivity (ρ) and resistance (R) of a conductor of length (L) and area (A).

(6) Electric power: Electric power is defined as the rate of consumption of energy or simply the rate of doing work.

i.e., power (P) = .

The SI unit of power is watts (W).