Electricity: Electric Potential Difference
These notes are based on the chapter Electricity class 10 science of NCERT book and CBSE syllabus.
- Mathematical expression of potential difference
- Symbols in electric circuit
The difference in the amount of electric potential energy between two points in an electric circuit is called ELECTRIC POTENTIAL DIFFERENCE or potential difference. Potential difference is known as voltage, which is equal to the work done per unit charge to move the charge between two points against static electric field.
Therefore,
`text(Voltage)=text(Work done)/text(Charge)`
Voltage or electric potential difference is denoted by V. Therefore;
`V=W/Q` -----------(1)
Where, W = work done and Q = Charge
SI unit of potential difference
SI unit of electric potential difference is volt and denoted by V. This is named in honour of Italian Physicist Alessandro Volta.
`V=text(Joule)/text(Coulomb)=J/C`
Or, `V=J C^(-1)`
Since joule is the unit of work and coulomb is the unit of charge, 1 volt of electric potential difference is equal to the 1 joule of work to be done to move a charge of 1 coulomb from one point to another in an electric circuit. Therefore,
`1V=(1 text(Joule))/(1 text(Coulomb))=(1J)/(1C)`
Voltmeter: An apparatus to measure the potential difference or electric potential difference between two points in an electric circuit.
Symbols used in a Circuit diagram
Fig: Common Symbols of Circuit Diagram
Symbol of electric cell
Symbol of electric cell is two small vertical lines. One of the lines is longer and thinner while another line is shorter and thicker. The longer and thinner line shows positive terminal of electric cell, and shorter and thicker line shows negative terminal of electric cell.
Symbol of battery
Symbol of battery is a series of symbols of electric cell. While making a symbol of battery it is important to alternate the thinner line with thicker line.
Symbol of electric wire
Symbol of electric wire is a straight line.
Symbol of electric switch
Symbol of electric switch is of two types. One type shows two lines with dots and a small gap between two dots. A small slanting line, leaving the gap open shows electric switch in off position. A line closing the gap shows electric switch in on position. Second type of symbol shows medium braces with lines jutting out of them. A dot is put inside the braces to show electric switch in on position.
Symbol of electric bulb
Symbol of electric bulb is a loop in the shape of letter M. In some circuit diagrams line drawing of electric bulb is also used.
Symbol of ammeter and voltmeter
Symbol of ammeter is A written inside a circle. Symbol of voltmeter is V written inside a circle.
Symbol of Resistance
Symbol of resistor is zig-zag line. Variable resistance is shown by an arrow across the symbol of resistor.
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