# Current

## Ammeter

An ammeter is used to measure **current**, measured in **Amps**, A. It is always placed in **series**.

## Current

Current is the **rate of flow of charge** and in metals it is the **flow of electrons.**

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## Equation

You must be able to remember and apply this equation: **charge flow = current x time**

This can also be written as: Q = It

- Q = Charge (Coulombs, C)
- I = Current (Amps, A)
- t = Time (Seconds, s)

Around a single loop the current always remains the same.

Let’s look at some examples:

Notice, in the second example, time is changed from minutes to seconds. Always use **seconds**!! Never minutes or hours.

Also, look at the three steps in showing ones working. You should always show your working, even if you use a calculator - and never forget to include units!

- What is the unit of Charge?
- Your answer should include: Coulomb / Coulombs / C
- Calculate the charge which passes a point in a circuit with a current of 10A in 45 seconds.
- 450C
- Calculate the current with 40kC of charge passing a point in 5ms. Hint: 1kC = 1000C 1millisecond = 0.001 second
- Your answer should include: 8 x 10^6 A / 8000000 A