20.2 Electric Current and Ohm’s Law Key Concepts What causes an electric current? What are some examples of conductors and insulators? What factors affect electrical resistance? How are voltage, current, and resistance related?

If one part isn’t functioning, the flashlight _______ light The different parts of a flashlight form a continuous path for through which charges can __________ If one part isn’t functioning, the flashlight _______ light flow won’t Flow of current Switch Negative terminals Spring Positive terminals

The continuous flow of electric charge is an electric ___________ The SI unit of electric current is the ampere _____, or _______, which equals 1 coulomb per second ______ current (A) C/s amp Flow of current Switch Negative terminals Spring Positive terminals

In direct current ______, charge flows in only ________ direction. A flashlight and most other battery-operated devices use direct current. In alternating current ______, a flow of electric charge regularly _______________ its direction. Electric current in your home and school is mostly alternating current. (DC) one (AC) reverses

Conductors and Insulators ____________such as copper and silver are good electrical ________________. A material through which charge can flow _____________. Wood, plastic, rubber, and air are good electrical ________________. A material through which charge ___________ flow easily. Metals conductors easily insulators cannot

Conductors and Insulators A metal wire is usually _____________ with plastic or rubber. . The coating around a wire helps to _____________ the current and keep it where it is needed. coated control

Resistance is _________________ to the flow of charges in a material. As electrons move through a conducting wire, they _______________ with electrons and ions. These collisions convert some kinetic energy into _____________ energy, and the current is ________________. The SI unit of resistance is the _______(Ω) opposition collide thermal reduced ohm

Resistance A material’s _______________, ____________, and _________________ affect its resistance. Resistance is ____________ in a longer wire because the charges travel ___________. As temperature increases, a metal’s resistance increases because electrons collide more ______________. thickness length temperature greater farther often

Using a thick straw to drink a milkshake is _____________ than using a thin straw. Similarly, electrons flow more easily through a ___________ wire than they flow through a thin wire of the same material. easier thick metal ions electron

Recall that potential energy is related to _____________. Voltage In order for charge to flow in a conducting wire, the wire must be connected in a complete ___________ that includes a _____________ of electrical energy. Recall that potential energy is related to _____________. The potential energy of a charge depends on its position in an electric ____________. loop source position field

Voltage Potential difference is the difference in electrical potential energy between _______ _______________ in an electric field. Potential difference is measured in joules per coulomb, or ____________. Because it is measured in volts, potential difference is also called __________________. two places volts voltage

Three common voltage sources are…. __________________ A source of voltage does _________ to increase the potential energy of electric charges. Three common voltage sources are…. __________________ work batteries solar cells generators

Batteries, like other voltage sources, have _________________ that can A battery is a device that converts _____________ energy into ______________ energy Batteries, like other voltage sources, have _________________ that can connect to ________ in a circuit A voltage ________, or potential difference, is maintained across the terminals chemical electrical terminals wires drop

Increasing the voltage ____________ the current. Ohm’s Law Increasing the voltage ____________ the current. Keeping the same voltage and increasing the resistance ________________ the current. increases decreases

Ohm’s Law According to Ohm’s law, the voltage (____) in a circuit equals the product of the current (____) and the resistance (______). V I R

Ohm’s Law What is the voltage if the resistance is 3 ohms and the current is 3 amps? V = 3 amps x 3 ohms = 9 volts

Ohm’s Law A ________________ can be used to measure current, voltage, or resistance. multimeter

Assessment Questions 1. If a piece of wire has a certain resistance, which wire made of the same material will have a lower resistance? a hotter wire a thicker wire a longer wire a thinner wire

Assessment Questions 2. What does the voltage between two points in an electric field represent? the total kinetic energy the difference in mechanical energy the difference in potential energy the electrical energy

Assessment Questions 3. A 9-volt battery drives an electric current through a circuit with 4-ohm resistance. What is the electric current running through the circuit? 0.44 A 2.25 A 5 A 36 A

Assessment Questions 4. The two types of electric current are direct current and indirect current. True False