Electricity flows through wires because of a special kind of “push” called potential difference, also known as voltage. This push helps move tiny particles called electrons from one place to another inside an electrical conductor, like a wire.
What is Potential Difference?
Potential difference is the energy needed to move a charge (electron) from one point to another in a circuit. It is measured in Volts (V).
Formula for Potential Difference
1 Volt=1 Joule / 1 Coulomb
This means that 1 volt is the amount of energy (1 Joule) required to move 1 unit of charge (1 Coulomb) through a circuit.
How Does It Work?
- Imagine rolling a ball down a hill. The ball at the top has more energy (potential energy), and as it moves down, this energy changes into motion (kinetic energy).
- Similarly, when a charge moves through a wire, its energy changes from one form to another, which is why electrical devices like bulbs and fans work.
The relationship between energy and potential difference is:
KE=Q×V
where:
- KE = Kinetic Energy
- Q = Charge
- V = Voltage (Potential Difference)
If a charge moves between two points A and B in a circuit, the potential difference is:
ΔV=ΔU / q
where:
- ΔV = Change in potential difference
- ΔU = Change in potential energy
- q = Charge
Potential Difference vs Electromotive Force (EMF)
Many people confuse potential difference with electromotive force (EMF), but they are different:
- Potential Difference (Voltage): The energy needed to move a charge between two points in a circuit.
- EMF: The energy supplied by a battery or power source to push the charge through the circuit.
Example
If a battery provides 9V, it means it supplies 9 Joules of energy to every 1 Coulomb of charge moving through it.
This is how voltage works to make electricity flow and power devices like lights, TVs, and mobile chargers!
Understanding Potential Difference in Simple Terms
Potential Difference, also known as Voltage, is defined as the work done per unit charge to move a test charge between two points in an electric circuit. It is an essential concept in electrical circuits and is responsible for driving electric current through a conductor. The SI unit of potential difference is the Volt (V).
When electric current flows through a circuit from point P to point Q, the charge between these points is important. The exact potential at each point is not necessary; instead, the difference in potential between these points gives us all the information we need. This difference is called the Potential Difference (Voltage).
The work done in transferring a 1-coulomb charge from one location to another determines the potential difference. If the work is 1 joule, then the potential difference between the two points is 1 volt.
1 volt=1 joule / 1 coulomb
Voltage Measurement
The volt is the unit of measurement for potential difference. To measure voltage in a circuit, we use a voltmeter.
When connecting the voltmeter, ensure that the positive terminal is connected to the positive terminal of the cell, and the negative terminal is connected to the negative terminal.
Ohm’s Law and Voltage
According to Ohm’s Law, the potential difference across a fixed resistance of 1 ohm with a current of 1 ampere flowing through it is equal to 1 volt. This can be mathematically expressed as:
V=I×R
Where:
- V = Potential Difference (Voltage)
- I = Current (in amperes)
- R = Resistance (in ohms)
The Origin of the Volt
The volt is named after the renowned physicist Alessandro Volta, who is credited with inventing the electric battery and making significant contributions to the study of electricity.
Key Points to Remember
- Potential Difference = Voltage
- Unit of Measurement: Volt (V)
- Formula: 1 volt=1 joule /1 coulomb
- Voltage Measurement Tool: Voltmeter
- Relation to Ohm’s Law: V=I×R
By understanding potential difference and its relation to electric current, you’ll be able to grasp the fundamentals of electricity and electrical circuits more clearly!
SI Unit of Potential Difference (Voltage)
The SI unit for measuring the work done per unit of charge is the volt (V). This is equivalent to one joule per coulomb.
While the volt was originally defined in terms of power and current, since 1990, the definition has expanded to include the quantum Hall effect and the Josephson effect.
In 2019, the SI units were redefined based on fixed values of physical constants, bringing more precision to our understanding of units like the volt.
Symbol and Standardization
In English-speaking regions, potential difference (voltage) is symbolized as ΔV (often simplified to V). However, the international standard symbol for voltage is U, and this symbol is used in various important electrical laws, such as Ohm’s Law and Kirchhoff’s Laws.
Electrochemical and Galvani Potential
Voltage, or potential difference, that can be measured directly using a voltmeter is known as the electrochemical potential. On the other hand, the Galvani potential occurs at junctions between different materials and affects the movement of charge but cannot be measured externally with a voltmeter.
Voltage and Charge Movement
Voltage plays a critical role in the movement of charged objects. It causes negatively charged objects to move towards areas of higher voltage and positively charged objects to move towards areas of lower voltage. As a result, conventional current in a conductor always flows from higher voltage to lower voltage.
Historical Terminology
Historically, voltage has been described using terms such as “tension” and “pressure”. The term “tension” is still commonly used today, especially in contexts like high tension (HT), which is often encountered in vacuum tube electronics and automotive systems.
The Volt: A Tribute to Alessandro Volta
The volt (V) is the derived unit for electric potential, voltage, and electromotive force (EMF). The unit is named after the Italian physicist Alessandro Volta (1745–1827), who is credited with inventing the voltaic pile, possibly the first chemical battery.
Difference Between Potential Difference and EMF
The key differences between Potential Difference and Electromotive Force (EMF) are as follows:
| Potential Difference | Electromotive Force (EMF) |
|---|---|
| Definition: The difference in potential between any two points in a closed circuit is termed as Potential Difference. | EMF is the maximum potential difference between the two electrodes of a cell when the circuit is open, i.e., no current is flowing. |
| Energy Dissipation: The energy dissipated when a unit charge flows through the components of the circuit is known as Potential Difference. | EMF is the energy supplied to the charge by the cell or power source. |
| Dependence on Resistance: The Potential Difference depends on the resistance between two points and is directly proportional to it. | EMF does not change with the resistance in the circuit. |
| Magnitude: The Potential Difference is always less than the EMF. | The EMF is always greater than the potential difference. |
| Field of Induction: The Potential Difference is induced only under electric fields. | EMF can be generated in electric, magnetic, and gravitational fields. |
| Formula: The formula for Voltage or Potential Difference is: |
Key Takeaways
- Potential Difference occurs within a circuit, whereas EMF is the potential difference when the circuit is open.
- EMF provides the energy needed to move the charge, while the Potential Difference results from the energy used in the circuit.
- The Potential Difference depends on the circuit’s resistance, but EMF remains constant regardless of the resistance.
By understanding these differences, you can better grasp the concepts of electric circuits, energy transfer, and the role of voltage in the flow of current.
