# Electric Current 6.2.

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Electric Current 6.2

Current and Voltage Difference
Electric Current-The net movement of electric charge in a single direction. Measured in Amperes (A) One Ampere is equal to 1 coulomb per second If there is no current, there is no NET movement Movement forward=movement backward=movement side-to-side When an electric current is applied, there is still backward and forward movement, but the electrons drift in the direction of the current. Net movement

Before Current is Applied
After Current is Applied

Current and Voltage Difference
Related to the force that causes electric charges to flow. From area of high voltage to low voltage Measured in volts (V) Electric Circuits A closed path that electric current follows Battery, wire, lightbulb Current and electron flow For historical reasons, we think of current as flow of positive charges Positive charges do not flow Due to this, current is in the opposite direction of electron flow Electrons flow from lower to higher voltage Current is from higher to lower voltage

Batteries 2 Main Types: Dry-cell Wet-cell

Dry-Cell Batteries Carbon Rod (positive) Zinc Container (negative)
Moist paste (electrolyte) Allows electrons to flow Batteries in flashlights Metals can be different Lithium, carbon, and lithium solution Cell phone battery

Wet-cell Battery 2 connected plates made of different metals in an electrolyte Unlike the paste in dry-cells, the wet-cell has a liquid Has many cells connected together. Most common type is lead-acid Lead and Lead dioxide in sulfuric acid solution

Electrical Outlets The 2 holes of an outlet have a voltage difference
In the U.S. usually 120 V

Resistance Tendency of object to resist flow of electrons
Takes some of the flowing electrons from the current Measured in ohms (Ω) This symbol is the capital form of the Greek letter “Omega” This is why batteries charging get warm The resistor is taking some of the electrons, and converts the chemical energy to thermal energy

Ohm’s Law Current(A)=Voltage difference(V)/resistance(Ω) 𝐼= 𝑉 𝑅
Current is measured in Amps (A) 𝐼= 𝑉 𝑅 Where I is current

Example Problem The voltage difference in a graphing calculator is 6V, and the resistance is 1,200 Ω. What is the current through the batteries of the graphing calculator? Knowns: V=6V, R=1200 Ω Unknown: I=? Equation: 𝐼= 𝑉 𝑅 Solve: 𝐼= 𝑉 𝑅 = 6𝑉 1200Ω =0.005 A

Equations Solve for V Solve for R

Guided Practice An object has a resistance of 60 Ω as a current of 2 A goes through it. What is the voltage difference across the object?

You Try It! The voltage in a device is 50 V, and the resistance is 5 Ω. What is the current in the device?

Types of Current Alternating Current (AC) Direct Current (DC)
Type found in household electrical outlets Changes direction Direct Current (DC) Found in battery-powered devices Does not change direction Converters change types (ACDC)