What is Current?

Objectives:

• State the two laws of electrostatic charges.
• Define coulomb.
• Identify the unit used to measure current flow.
• Define the relationship of amperes, coulombs, and the time through a formula.
• Describe how current flows in a circuit.
• Describe how electrons travel in a conductor.
• Define and use scientific notation.
• Identify commonly used prefixes for powers of ten.

First Law of Electrostatic Charges

Like charges repel each other. ( + repels + , - repels - )

Second Law of Electrostatic Charges

Unlike charges attract each other. ( + attracts - )

Coulomb (C)

• Represents a specific quantity of electrons.
• Unit adopted for measuring charges.
• $6.24 \times 10^{18}$

Current (I)

Electrical current is the flow of electric charge.

In a conductor, the moving particles that carry the electric charge are electrons. They drift from the ➖negative terminal (excess of electrons) toward the ➕positive terminal (lack of electrons) when a voltage (potential difference) is applied.

Amperes (A)

• Unit of measure for current. It measures the rate at which electric charge flows. Think of it as the "flow rate" of the charge.
• It tells us how much charge flows through a wire every second.
• 1 ampere = 1 coulomb of charge passing a point in 1 second.

The relationship between amperes and coulombs can be expressed as:

$$I = \frac{Q}{t}$$

Where:

• $I$ is the current in amperes (A).
• $Q$ is the charge in coulombs (C).
• $t$ is the time in seconds (s).

success

Tip: cover the element you want to get.

• $Q = I \times t$
• $I = \frac{Q} {t}$
• $t = \frac{Q} {I}$

     Q
    / \
   /   \
  I --- t

• Milliampere (mA) = 1/1000 A or 0.001 A
• Microampere (µA) = 1/1,000,000 or 0.000001 A

Voltage (V)

• Supplies electrons from one end of the conductor.
• Removes electrons from the other end of the conductor.
• The difference in potential between two points in a circuit is called the voltage (V).

Scientific Notation

• Use single-digit number plus powers of 10 to express and small numbers.

Prefixes

• $10^3$ is called K, kilo
• $10^6$ is called M, mega
• $10^9$ is called G, giga
• $10^{12}$ is called T, tera

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• $10^{-3}$ is called m, milli
• $10^{-6}$ is called $\mu$, micro
• $10^{-9}$ is called n, nano
• $10^{-12}$ is called p, pico