Edexcel A Level (IAL) Physics-2.32 Electric Current- Study Notes- New Syllabus

Electric Current as Rate of Flow of Charge: \( I = \dfrac{\Delta Q}{\Delta t} \)

Electric current is a fundamental concept in electricity. It describes how quickly electric charge flows through a circuit.

Definition of Electric Current

Electric current is the rate of flow of charged particles (usually electrons) through a point in a circuit.

\( I = \dfrac{\Delta Q}{\Delta t} \)

• \( I \) = current (A)
• \( \Delta Q \) = charge flowing (C)
• \( \Delta t \) = time taken (s)

Key idea: 1 ampere = 1 coulomb of charge passing a point per second.

 Microscopic View: What Actually Flows?

• In metals, current is due to negatively charged electrons.
• In solutions and gases → ions carry charge.
• Current direction is defined as the direction of positive charge flow (conventional current).
• Electron flow is in the opposite direction.

Relationship With Drift Velocity

Using the drift velocity equation connects macroscopic current to the movement of electrons:

\( I = nqvA \)

This reinforces that current depends on:

• Number of charge carriers \( n \)
• Charge of carriers \( q \)
• Drift velocity \( v \)
• Cross-sectional area \( A \)

Understanding Charge Flow

• If more charge flows in the same time, current increases.
• If the same amount of charge flows in less time, current increases.
• Current measures how fast charges are moving past a point.