What is Unit of Voltage - SI Unit of Voltage
Voltage can be defined as the electric potential between two points. In a conductor, if the electric field is uniform, the potential difference between the points is,
V = EL
By using various equations of resistivity, current, and resistance, another equation can be derived,
V = EL
V = የJL
V = የ \[(\frac {I} {A})\] L
V = I \[(\frac {\varphi L} {A})\]
V = IR
From the above equation, we can deduce that the voltage or the potential difference across the resistor can be found by multiplying the current with the resistance. The unit of potential difference is Volt (V) which is also equal to Joule per Coulomb (J/C).
SI Unit of Voltage
The SI unit for voltage is Volt and is represented by the letter v. volt is a derived SI unit of electromotive force or electric potential. Thus, due to this volt can be defined in a number of ways. Volt can be defined as ‘the electric potential present along with a wire when an electric current of one ampere dissipates the power of 1 watt (W).
V = \[\frac {W} {A}\]
Also, volt can be expressed as the potential difference that exists between two points in an electric circuit which imparts energy of 1 joule (J) per coulomb of charge that flows through the circuit.
V = \[\frac {potential energy} {charge}\]
V = \[\frac {J} {C}\] = kg m2/As3
It can also be expressed as ampere times ohm, joule per coulomb or watt per ampere.
V = AΩ = \[\frac {W} {A}\] (energy per unit charge) = J\[\frac {J} {C}\] (power per unit current)
It can also be expressed as it is given in its SI unit,
1 V = 1 kg m2 s-3 A-1 (One-kilogram meter squared per second cubed per ampere).
Below are Some Other Electrical Units
Voltage Source
A voltage source is basically a device that is used in electric circuits having fixed potential differences at both ends. The voltage source can be a battery or any other source which has fixed potential difference and direct current.
(Image will be uploaded soon)
In case the ends of the voltage source are connected to a circuit that has multiple numbers of resistors, voltmeters, etc then a complete circuit is formed and the current can now flow from one end to the other. And if the current is flowing, then it is the same on both the terminals of the voltage source.
A voltage source is a part of a complete circuit that can produce an electromotive force. Electromotive force is represented using the symbol ε. The unit of electromotive force is the same as voltage, that is it is volt. Here volt is equal to a joule per coulomb (J/C). In the case of an ideal source, the electromotive force is equal to the voltage difference,
ε = V = IR
Real sources such as batteries are not considered ideal sources as they have some source of internal resistance. If r denotes the internal resistance of a battery, then the voltage difference present across the battery is,
V = ε - Ir
This can also be called the terminal voltage of the battery. When a complete circuit is made using a resistor that has resistance R, then the current flowing through can be found using the equation,
V = IR
IR = ε -Ir
IR + Ir = ε
I (R + r) = ε
I = \[\frac {(R+r)} {\epsilon}\]
Thus, the current is equal to the electromotive force of the source divided by the total resistance present in the circuit.
SI Unit of Voltage
SI or System International units is an international system of measurement that is used universally in all technical and scientific research.
SI units make sure that the students do not get confused while reading about units. A standard unit system helps the entire world understand all the measurements in just one set of unit systems. The SI unit of voltage is volt and is denoted by the letter v.
FAQs on Unit of Voltage
1. What is the SI unit of voltage and how is it defined?
The SI unit of voltage is the volt (V). One volt is defined as the potential difference between two points when one joule of energy is used to move one coulomb of charge between those points. Mathematically, 1 V = 1 J/C.
2. How is voltage related to current and resistance in a circuit?
According to Ohm's Law, voltage (V) across a conductor is directly proportional to the current (I) flowing through it and the resistance (R) of the conductor. This relationship is given as: V = I × R, where V is in volts, I in amperes, and R in ohms.
3. What is electromotive force (emf) and how does it differ from terminal voltage?
The electromotive force (emf) is the maximum potential difference provided by a source when no current is flowing. It is represented by the symbol ε. The terminal voltage across a real battery is slightly less than the emf due to internal resistance. The relationship can be expressed as: V = ε - Ir, where r is the internal resistance and I is the current.
4. Why is it important for students to understand the unit of voltage in Physics?
Understanding the unit of voltage is essential because it helps students interpret circuit diagrams, solve numericals, and relate theoretical concepts to real-world electrical systems. Mastery of this concept prepares students for board exams and further studies in Physics and engineering fields.
5. Describe two ways to express the unit of voltage using basic SI units.
The volt can be expressed in basic SI units as kg·m2·A-1·s-3. Another way to express volt is as watt per ampere (W/A) or joule per coulomb (J/C).
6. How does uniform electric field influence the calculation of voltage across a conductor?
In a uniform electric field (E), the potential difference or voltage (V) between two points separated by a distance (L) is given as V = E × L. This means that the voltage equals the strength of the electric field multiplied by the distance between the points.
7. What are common misconceptions students have regarding voltage and its measurement?
One common misconception is that voltage can exist at a single point; in reality, voltage is always measured between two points. Another is confusing voltage with current; while current is the flow of charge, voltage represents the energy per charge needed to move charges between two points.
8. How are units like volt, ohm, and ampere interrelated in circuit equations?
These units are interconnected through Ohm's Law: volt (V) represents potential difference, ampere (A) represents electric current, and ohm (Ω) represents resistance. The formula V = I × R shows how these quantities relate in every electrical circuit.
9. In what real-life situations is understanding the unit of voltage essential?
Understanding voltage is crucial in applications such as household wiring, operating electrical appliances, charging batteries, and troubleshooting circuits. It ensures safety and helps in selecting devices that function within specified voltage ratings.
