Part of Terms in the Electrical Field

HIMALAYAL - SHANGHAI - CHINA

I. Current   

Influenced by electric field force, free electrons do regular movements, forming the current. 

The direction at which positive charge moves is regarded as the direction of the current. The speed is 300,000km per second. The current intensity is represented by the quantity of electricity flowing through the conductor section per second. The unit is ampere (represented by the letter A). 1A current (I) means that the quantity of electricity (Q) flowing through 1C conductor section per second (T).  

Calculation formula: 

I=Q/T   1A=1C/1S

2. Voltage 

The voltage is the difference in electric potential between two points in the electric field, which is used to measure the energy difference generated by unit charge owing to different electric potentials in the static electric field. It equals to the work done by unit positive load moving from point A to point B. In terms of voltage direction, it is regulated that high electric potential points to low potential. 

The voltage is represented by U. The Volt (V for short) is the unit of voltage in the international system of units. Common units consist of mV, uV and kV etc. This definition is similar to the "water pressure" definition. However, in most cases, the "voltage" is used in the circuit while the "electric potential difference" is generally applied in all electrical phenomena.  

Calculation formula: 

1Vot=1J/1C    U=W/Q  

3. Ectrical Resistance

The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor. It is represented by the letter R. Its calculation unit is Ω. 

The conductor's numerical value of the resistance is proportional to the length of the conductor (L) and is inversely proportional to cross section area (S). Moreover, it is related to metal variety.  

R = pL/S    

Where:

R — resistance (Ω)

L — length (m) 

R — cross section area (cm2) 

p— resistance rate of the conductor, also referred to as resistance coefficient (Ω·m)