1) Charge is measured in coulombs, where 1 coulomb is equal to approximately 6.25 x 10^18 electrons. 2) Electric current is the rate at which charge flows through a circuit. It is measured in amperes and calculated by dividing the total charge by the time taken. 3) Current can be dangerous, with as little as 6 milliamperes being enough to stop a person's heart. Fuses and circuit breakers are used to prevent too much current in a circuit.

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?
Charge = number of e-
6.25 x 1018 e-
= 7.5 x 1021 e-
6.25 x 1018 e-
= 1.2 x 103 C
.: the charge is 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?
I = Q
T
= 240 C
300 s
= 0.8 A
.: the current is 0.8 A