1. What is an electric current?-
When a conductor acquires an excess or a deficit of electrons, we say it has an electric charge.
Due to the attraction and repulsion of electric charge, the electrons try to evenly distribute themselves around the conductor. To do this, the electrons have to move.

2. The movement of electric charges is known as electric current.

3. Electricity - electrons moving through a metal wire.

4. How is electric current measured?
Electric current is defined as the amount of charge that moves past a given point in a conductor per second.
Imagine you are standing beside a wire and can see the electrons moving from left to right. As you count the electrons going by, you determine that 100 electrons go by in 10 s.

5. From this information, the current in the wire can be calculated as 10 electrons/s.

6. Since electrons are very small and billions flow by in a second, we need to use a unit for quantity of electrons (or electric charge) that describes larger numbers of electrons.
This unit is called the coulomb (C), which represents 6.25 x 1018 electrons.

7. We can write electric charge mathematically . . .
I represents the electric current in amperes (A)
Q represents the total charge in coulombs (C)
∆t represents the elapsed time in seconds (s)

8. So, an electric current of 1 A occurs when 1 C of charge passes a point in a conductor in 1 s:

9. Be careful not to confuse the symbols for current, time and quantity of electrons (charge) with the units match each quantity:
I is the symbol for current; current is measured in units called amperes , A
Q is the symbol for quantity of charge; quantity of charge is measured in units called coulombs, C
∆t is the symbol for elapsed time; elapsed time is measured in seconds, s

11. Example: Calculate the amount of current through an electric toaster if it takes 1000 C of charge to toast 2 slices of bread in 2.0 minutes.

12. Example: Calculate the amount of current through an electric toaster if it takes 1000 C of charge to toast 2 slices of bread in 2.0 minutes.

13. Data: C
- 2 slices of toast
- 2 minutes (120 seconds)
2. Equation: I = C/s
3. Substitute: I = 1000/120
4. Calculation: A
5. Answer: Therefore, it takes 8.3 A to toast 2 slices of bread in 2 minutes.