When charge flows in a material, it's called an electric current. Imagine a highway of tiny, speedy particles!

• Unit: ampère (A)
• Hint: In the English-speaking world, it's often just written as "A" without the fancy accent.

Imagine a busy highway (the conductor). Each car represents an electron. If 1 billion cars (equivalent to one coulomb of electrons) pass a toll gate (point P) in 1 second, the traffic flow is equivalent to 1A. If it takes them 2 seconds, the flow is only half, or 0.5A. If they speed by in just 0.1 seconds, it’s a whopping 10A!

Equation: I = \(\frac{Δq}{Δt}\)  where Δq is the charge, and Δt is the time taken.

• In 2019, the definition of an ampere was updated. It's now: One coulomb flowing for one second.
• 1 electron carries a charge of 1.602176634 × 10⁻¹⁹C. This is super tiny, which is why 1 coulomb involves sooo many electrons.