Education Journalist | Study Abroad Lead
Unit of Voltage is volt which is also represented by the symbol “v.” The volt is basically a derived SI unit of electric potential or electromotive force. This is the reason why volt can further be defined in several ways. Voltage is the total force required to transfer a unit of charge between two points in a static electric field. In order to determine the voltage between two points, both static electric field and dynamic electromagnetic field should be assumed.
Read More: NCERT Solutions Chapter 3 Current Electricity
| Table of Content |
Key Terms: Voltage, Volt, Electrical Units, Electric Field, Electromotive Force, Conductor, Resistance, Current, Electromagnetic Field, Electric potential
What is Voltage?
[Click Here for Sample Questions]
The electric potential between two points is defined as voltage. In other terms, it is the work done in moving a charge from one pole to another through a wire. Both a static electric field as well as a dynamic electromagnetic field is considered to determine the voltage between any two points.
If the electric field is uniform in a conductor, the potential difference between the points can be expressed as,
| V = EL |
Another equation may be obtained by using resistivity, current, and resistance formulae:
V = EL
⇒ V = 
JL
⇒ V = (I/A)L
⇒ V = I ( L/A)
⇒ V = IR
We may conclude from the equation that multiplying the current by the resistance gives the voltage or potential difference across the resistor. Volt (V) is the unit of potential difference, which is also known as Joule per Coulomb (J/C).
Values of Voltage
Here are some of the important parameters of Voltage:
| Voltage Parameters | Values |
|---|---|
| Symbol of voltage | V, ΔV |
| SI unit of voltage | Volt |
| Dimension of voltage | ML2T-3I-1 |
Types of Voltage
Mainly, there are two types of voltage sources, and both of them are independent voltage sources and dependent voltage sources.
The two types of independent voltage sources are:
- Alternating voltage source
- Direct voltage source
The two types of dependent voltage sources are:
- Voltage controlled voltage
- Current-controlled voltage
Discover about the Chapter video:
Current Electricity Detailed Video Explanation:
Read More:
| Important Topic Related to Links | ||
|---|---|---|
| Meter Bridge | Potentiometer | Cells In Series and Parallel |
| Electromotive Force | Carbon Resistor | Types of Current |
| Electrical Current | Circuit Diagram | Electrical Charges |
What is the SI Unit of Voltage?
[Click Here for Previous Year Questions]
Volt is the SI unit of electromotive force or electric potential and is represented by the letter V. As a result, volt can be defined in a variety of ways. The electric potential existing along with a wire when an electric current of one ampere dissipates the power of one watt is defined as a volt (V).
| W/A = V |
Volt may also be defined as the potential difference between two points in an electric circuit that imparts 1 joule (J) of energy per coulomb of charge flowing through the circuit.
V = potential energy/ charge
⇒ V = J/ C
Unit of Voltage = Kg m2/ A s3
Voltage can also be expressed in Ampere times ohm, joule per coulomb, and watt per ampere.
V = AΩ = W/A (energy per unit charge) = J/C (power per unit current)
It can also be represented in SI units, as follows:
| 1 V = 1 kg m2s-3A-1 |
Some of the very common sources of voltage are batteries and generators. Voltage (also known as electric potential difference, electric pressure or electric tension) can simply be defined as the difference in electric potential between two points, which (within a static electric field) is expressed as the work required per unit of charge to move a test charge between the two points.
What can happen to the power if voltage is increased?According to the formula of power, it can be said that power is the product of voltage and current. Simply, current is inversely proportional to voltage assuming that power is constant. Hence, if the voltage is increased, power will also proportionally increase given that current is constant. Define ideal voltage source.Ideal voltage source can be expressed as the two-terminal element wherein the voltage across terminals is defined at every instant of time. Besides, voltage is independent of the current via the source, i.e., the current can flow in any and every direction via the source. |
Other Important Electrical Units
[Click Here for Sample Questions]
The following are some of the other electrical units:
| Electrical Parameter | SI Unit | Symbol |
|---|---|---|
| Charge | Coulomb | Q |
| Impedance | Ohm | Z |
| Conductance | Simen | G or |
| Capacitance | Farad | C |
| Inductance | Henry | L or H |
| Voltage | Volt | V or E |
| Power | Watts | W |
| Frequency | Hertz | Hz |
| Resistance | Ohm | R or Ω |
Voltage Source
[Click Here for Previous Year Questions]
A voltage source is a device used in electric circuits with a set potential difference between the two ends. A battery or any other source with a set potential difference and direct current can be used as the voltage source.
If the ends of the voltage source are linked to a circuit with numerous resistors, voltmeters, and other components, a full circuit is established and current may now flow from one end to the other. And if the current is flowing, it is the same on both the voltage source's terminals.
A voltage source is a component of a circuit that may generate an electromotive force. The electromotive force is denoted by the symbol ε.
The unit of electromotive force is the volt, which is the same as the unit of voltage. In this case, a volt is equaled to a joule per coulomb (J/C). The electromotive force is equal to the voltage difference in the case of an ideal source.
ε = V = IR
Real sources, like batteries, are not perfect sources since they have some internal resistance. If r is the internal resistance of the battery, then the voltage difference across the battery can be expressed as:
V = ε - Ir
This is often referred to as the battery's terminal voltage. When a full circuit is constructed using a resistor of resistance R, the current passing through may be calculated using the equation,
| V = IR |
⇒ IR = ε -Ir
⇒ IR + Ir = ε
⇒ I (R + r) = ε
⇒ I = (R + r)/ ε
As a result, the current is equal to the electromotive force of the source divided by the total resistance in the circuit.
Things to Remember
- Voltage is the force required to transfer a unit of charge between two points in a static electric field.
- It is also defined as the electric potential between two points.
- The electric potential difference, electric pressure, electromotive force (emf), and electric tension are all used to describe voltage.
- Mathematically Voltage is expressed as, V = EL and V = IR.
- SI unit of voltage or electromotive force or electric potential is Volt and it is represented by the letter V.
- Other Units of Volatge are- Kg m2/ A s3 and kg m2 s-3 A-1
- A voltage source is a device used in electric circuits with a set potential difference between the two ends.
- The electromotive force is equal to the voltage difference in the case of an ideal source. It is expressed as: ε = V = IR
Read More:
Previous Year Questions
- Figure shows currents in a part of an electric circuit, then current I is….[KCET 2000]
- Calculate the net resistance of the circuit between A and B ….[NEET 2000]
- If specific resistance of a potentiometer wire is 10−7Ωm and….[NEET 2001]
- Copper and silicon is cooled from 300 K to 60 K, the specific resistance….[NEET 2001]
- In the circuit shown in figure, neglecting source resistance, the voltmeter and ammeter readings will respectively be...[KCET 2001]
- In the electric network shown, when no current flows through the 4Ω resistor…
- In the above circuit the current in each resistance is….
- Find the internal resistance of the cell....[JEE Mains 2018]
- In vertical circular motion, the ratio of kinetic energy of a particle…. [MHT CET 2016]
- The motion of a particle in straight line is…. [JKCET 2013]
- A charged particle enters a uniform magnetic field with a certain speed …. [JKCET 2006]
- From the top of a tower a body AA is projected vertically up…. [JKCET 2007]
- The potential difference per unit length of the wire will be… [ NEET 1999 ]
- Value of R for which the power delivered in it is maximum is given by... [ NEET 1992 ]
- In the circuit shown, current (in A) through the 50 V and 30 V batteries are, respectively…..[JEE Main 2014]
Read More:
Sample Questions
Ques: Mention some common voltage sources. (1 Mark)
Ans: Batteries and generators are the most frequent voltage sources.
Ques: Ques: When the voltage is raised, what happens to the current? (1 Mark)
Ans: The electrical current, I, is proportional to the voltage, V, and inversely proportional to the resistance, R, according to Ohm's law. As a result, as voltage rises, the current rises, as long as the circuit's resistance remains constant.
Ques: What happens to the current when the voltage is raised? (1 Mark)
Ans: The electrical current, I, is proportional to the voltage, V, and inversely proportional to the resistance, R, according to Ohm's law. As a result, as voltage rises, the current rises, as long as the circuit's resistance remains constant.
Ques: When the voltage is raised, what changes can be seen in power? (1 Mark)
Ans: We may deduce from the power formula that power is the product of voltage and current. When power is constant, the current is inversely proportional to the voltage, according to the definition. As a result, if the voltage is increased while the current remains constant, power will increase correspondingly.
Ques: What is an ideal voltage source? (1 Mark)
Ans: A two-terminal element is described as an ideal voltage source when the voltage across these terminals is specified at every moment of time. Furthermore, voltage is unaffected by the current flowing through the source, which means the current can flow in either direction.
Ques: A voltmeter is to be connected to the circuit to measure the potential difference across a conductor. Mention the type of combination in which it should be connected with the conductor. (1 Mark)
Ans: The voltmeter should always be connected in parallel across the conductor.
Ques: (a) What is the least count of the voltmeter?
(b) In a voltmeter there are 20 divisions between the ‘0’ mark and 0.5 V mark. Calculate its least count. (2 Marks)
Ans: (a) The least count of the voltmeter is defined as the minimum potential difference measured by a voltmeter between the two given terminals.
(b) Given marks of the voltmeters = 0 and 0.5 V
Potential difference = 0.5 - 0 = 0.5V
No. of divisions between these two marks = 20
Ques: Define 1 volt. Express it in terms of SI unit of work and charge calculate the amount of energy consumed in carrying a charge of 1 coulomb through a battery of 3 V. (3 Marks)
Ans: When 1-joule work is done to carry 1 coulomb of charge from infinity to a fixed point in the electric field, then the potential at that point is called 1 volt.
The potential difference between the two points is
Ques: (a) Define the term ‘volt’.
(b) State the relation between work, charge, and potential difference for an electric circuit. Calculate the potential difference between the two terminals of a battery if 100 J of work is required to transfer 20 C of charge from one terminal of the battery to the other. (3 Marks)
Ans: (a) When 1 joule of work is done to carry 1 coulomb of charge from infinity to a point in the electric field, then the potential at that point is called 1 volt.
(b) Potential difference, V = Work done on unit charge = W/q
Given that: Work = 100 J
q=20oC
Potential difference,
V = W/q
V=100/20
Potential Difference (V) =5V
Ques: (a) Calculate the resistance of 1 km long copper wire of radius 1 mm. The resistivity of the copper is 1.72 x 10-8 ? m.
(b) Draw a schematic diagram of a circuit consisting of a battery of three cells of 2 V each, a 5Ω resister, an 8Ω resistor, and a 12Ω resistor and a plug key, all connected in series. (3 Marks)
Ans: 
Ques: Draw a schematic diagram of an electric circuit consisting of 3 cells and an electric bulb, ammeter, plug-key in the ON mode, and another with the same components but with two bulbs in parallel and a voltmeter across the combination. (2 Marks)
Ans: Figure 1 shows the schematic diagram of an electric circuit comprising of 3 cells and an electric bulb, ammeter, plug-key in the ON mode and figure 2 shows a schematic diagram of an electric circuit comprising of 3 cells and two electric bulbs in parallel, ammeter, plug-key in the ON mode and voltmeter across the combination.
Ques: Two resistors R1 and R2 may form (i) a series combination or (ii) a parallel
combination, and the combination may be connected to a battery of 6 volts. In which combination, will the potential difference across R1 and across R2 be the same and in which combination, will the current through R1 and through R2 be the same?
(b) For the circuit shown in this diagram, calculate
(i) the resultant resistance.
(ii) the total current.
(iii) the voltage across 7Ω resistor. (5 Marks)
Ans: (a) If R1 and R2 are connected in parallel combination then the potential difference across R1 and R2 is the same and when R1 and R2 are connected in series then the current through them is the same.
(b) 
Ques: Name a device that you can use to maintain a potential difference between the ends of a conductor. Explain the process by which this device does so. (Board Term I, 2013)
Ans: A cell or a battery can be used in order to maintain a potential difference between the ends of a conductor. The chemical reaction within a cell generates the potential difference across the terminals of the cell, even when no current is drawn from it. When it is connected to a conductor, it produces electric current and, maintain the potential difference across the ends of the conductor.
For Latest Updates on Upcoming Board Exams, Click Here: https://t.me/class_10_12_board_updates
Also Read:
Comments