Voltage

Electricity
definition

Also known as: potential difference, EMF, V

Grade 6-8

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The difference in electric potential energy per unit charge between two points. Without voltage, there's no current — voltage is the driving force of every circuit.

Definition

The difference in electric potential energy per unit charge between two points. Measured in volts (V).

💡 Intuition

Voltage is like water pressure — it's the 'push' that drives current through a circuit.

🎯 Core Idea

Voltage is the energy per coulomb available to push charges through a circuit.

Example

A AA battery provides 1.5 V. A wall outlet provides 120 V (or 230 V in many countries). That's why outlets are more dangerous.

Formula

V = \frac{W}{Q} where W is energy (work) and Q is charge.

Notation

V is voltage in volts (V = J/C), W is work or energy in joules, Q is charge in coulombs, \vec{E} is the electric field, and d\vec{l} is an infinitesimal path element.

🌟 Why It Matters

Without voltage, there's no current — voltage is the driving force of every circuit.

💭 Hint When Stuck

When solving a voltage problem, first identify the two points between which the potential difference is measured. Then use V = W/Q if energy and charge are given, or V = IR (Ohm's law) if current and resistance are known. Finally, check the direction: current flows from higher to lower potential through a resistor.

Formal View

Voltage (potential difference) between two points is V = \frac{W}{Q} = -\int_A^B \vec{E} \cdot d\vec{l}, where W is the work done per charge Q. In circuits, Kirchhoff's voltage law states \sum V = 0 around any closed loop.

🚧 Common Stuck Point

Voltage exists between two points (it's a difference), not at a single point.

⚠️ Common Mistakes

  • Saying 'the voltage through a component' — voltage is across (between two points), not through; current flows through components.
  • Thinking voltage is used up as current flows — voltage drops across each component, but the total drop around a loop equals the source voltage (Kirchhoff's voltage law).
  • Confusing EMF (the energy supplied per coulomb by a source) with terminal voltage (which is lower due to internal resistance).

Common Mistakes Guides

Electric Current

Frequently Asked Questions

What is Voltage in Physics?

The difference in electric potential energy per unit charge between two points. Measured in volts (V).

What is the Voltage formula?

V = \frac{W}{Q} where W is energy (work) and Q is charge.

When do you use Voltage?

When solving a voltage problem, first identify the two points between which the potential difference is measured. Then use V = W/Q if energy and charge are given, or V = IR (Ohm's law) if current and resistance are known. Finally, check the direction: current flows from higher to lower potential through a resistor.

Prerequisites

electric current

How Voltage Connects to Other Ideas

To understand voltage, you should first be comfortable with electric current. Once you have a solid grasp of voltage, you can move on to resistance, ohms law and potential difference.

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