1) Charge is measured in coulombs, with one coulomb equal to approximately 6.25 x 1018 electrons. Current is a measurement of the rate of flow of electric charge, measured in amps. 2) Current is calculated by taking the total charge passed and dividing by the time taken. An ammeter is used to measure current in a circuit. 3) Common units for charge, current, and time are coulombs (C), amps (A), and seconds (S) respectively. The equation for calculating current is I = Q/T, where I is current in amps, Q is charge in coulombs, and T is time in seconds.

1. Quantifying Electricity:
Charge and Current

2. Quantifying Electricity
Charge: Electrons do not travel alone. Instead, they
travel in big groups called Coulombs.
A big group
1 e- of e-

3. Charge
Every Coulomb is an amount of negative
charge equal to 6.25 x 1018 electrons.
1 Coulomb
(imagine many electrons)

4. Charge
Symbol for Charge: Q
Unit of Measurement: Coulomb (C).

5. Charge
For example, if we say that the charge going
through a load is 50 Coulombs, then
Q = 50 C

6. Try This.
There are 6.25 x 1018 electrons in 1 Coulomb.
There are
6 250 000 000 000 000 000 electrons
in 1 Coulomb.

7. Calculating Electric Current
Charge = number of e-
6.25 x 1018 e-
Name Unit Symbol
Charge Coulomb Q

8. Try This.
(Problem Set Charge Question #1)
A hair dryer has 7.5 × 1021 electrons passing through it.
How much charge is in the hair dryer?
Answer: 1.2 x 103 C

9. Quantifying Electricity
Electric Current: The rate of movement of electric charge
(Coulombs) from one place to another.

10. Current
A fuse (or circuit breaker) is a connector in a circuit that is
designed to open the circuit if there is too much current.
Symbol for fuse
Breakers Fuses

11. Current
An ammeter is a device that is used to
measure current in a circuit.
Symbol for
ammeter Ammeter

12. Current
Current is dangerous and can seriously harm a person.
It only takes 6 mA to reach the heart to kill a person.

13. Electric Current
Symbol for Current: I
Unit of Measurement: Ampere (A) or just Amp.

14. Electric Current
For example, if we say that the current going
through a load is 10 Amperes, then
I = 50 A

15. Calculating Electric Current
Current = Charge
Time
Ampere = Coulomb
Second
I = Q
T
Name Unit Symbol
Current Ampere I
Charge Coulomb Q
Time Second T

16. Try This.
(Problem Set Current Question #4)
If 240 C of charge passes a point in a circuit in 300 s,
what is the current through that point in the circuit?
Answer: 0.8 A