Current
Current is the flow of charge: I = Q/t.
About this topic
Electric current is the rate of flow of charge, I = Q/t, in amperes (1 A = 1 C/s). In metals it's electrons drifting, but conventional current is defined as the direction a positive charge would flow, from + to −.
Current is measured by an ammeter placed in series. The same current flows through all parts of a series circuit, while it splits in a parallel one. For example, a phone charger delivering 2 A for 10 minutes moves 2 × 600 = 1200 coulombs of charge.
Electrons drift very slowly, often less than a millimetre per second, yet the lamp lights instantly because the electric field is set up through the whole wire at nearly the speed of light, like water already filling a pipe.
Currents of about 0.1 A through the body can be fatal. A frequent misconception is that current gets used up as it goes round a circuit; in fact the same charge keeps circulating, and it is energy that is transferred to components.
Key ideas
- Measured in amperes
- Conventional current flows + to −
- Electrons drift the other way
Quick check
Use cases: where Current helps
- Homework: review the key idea behind Current before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Current without notes.
- Visual learning: play with the interactive lab to see how Current changes when you adjust its inputs.
- Teaching a friend: explain Current in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Current?
Current is the flow of charge: I = Q/t.
What will I learn in Current?
Measured in amperes. Conventional current flows + to −. Electrons drift the other way.
Is Current part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Current lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Current?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.