Voltage in Electric Circuits

Voltage (also called electric potential difference) is the cause of electric current in a circuit. It tells us how much energy each unit of charge gains or loses when moving through the circuit.

In simple terms, voltage is the "push" that makes electric charges (usually electrons) move through wires and components.

In a circuit, voltage is supplied by a power source like a battery or generator. It provides the energy per charge needed to move electrons through the circuit.

🧮 What is a Volt?

The volt (V) is the SI unit of voltage.One volt is defined as the potential difference that gives one joule (J) of energy to one coulomb (C) of charge.

  1 volt = 1 joule / 1 coulomb

So, if a battery provides 9 volts, that means it gives 9 joules of energy to each coulomb of charge.

🧲 What is an Electron?

An electron is a tiny subatomic particle with a negative electric charge (−1.6 × 10⁻¹⁹ coulombs).Electrons are the main particles that move in wires to form electric current.

In conductors like copper, electrons are loosely bound and can move freely when a voltage is applied.

🔋 Voltage and Potential Difference

Potential difference is another name for voltage. It refers to the difference in electric potential energy between two points in a circuit.

Electric potential is like height in a water system:

• A battery makes one side “higher” (positive) and the other “lower” (negative).

• Electrons “flow downhill” from low potential to high (though current is considered to flow from high to low, by convention).

  
  

⚙️ Electromotive Force (EMF)

Electromotive force (emf) is the maximum potential difference that a source like a battery or generator can provide when no current is flowing.

Even though it's called a "force," it is actually a type of voltage — the total energy per charge provided by the source.When the circuit is active, the actual voltage across the terminals might be slightly less than the emf due to internal resistance inside the battery.

🔍 How is Voltage Measured?

Voltage is measured using an instrument called a voltmeter.

• It is connected in parallel across the two points where voltage needs to be measured.

• A voltmeter has very high resistance so that it does not draw current from the circuit.

For example, to measure the voltage across a light bulb, you connect the voltmeter's probes to both ends of the bulb.

🔌 Summary of Concepts in Scientific Terms:

• Voltage is the energy per unit charge, causing current.

• Volt is the unit of voltage, defined as joule per coulomb.

• Electron is the negatively charged particle that moves to create current.

• Potential difference is the change in potential energy per charge between two points.

• Electromotive force (EMF) is the source voltage when no current flows.

• Voltmeter is used to measure voltage and is always connected in parallel.