Electric Current Chapter 34 Electric Current n Electrons

Electric Current Chapter 34

Electric Current n Electrons in motion. n Current: The number of electrons that pass a specific point in a circuit in one second I = Q/t n Circuit: electric current flows through a closed, continuous path.

Electric Current n The reason electric charge flows from one place to another is voltage. a. Voltage is the difference in electrical potential between two places where e¯ are flowing. b. Voltage is the “push” that makes electric charges move. c. Measured in volts (V). HIGH LOW

Batteries are e¯ pumps. a. They provide a voltage difference to a circuit. b. Types: wet-cells & dry-cells

Generating Electric Current Electrochemical cell: (battery) changes chemical energy into electric energy. Two types wet cell and dry cell. n Thermocouples: a tool that uses differences in temperature to generate electric currents. n Generator- next chapter but make alternating current n

Types of current Direct current: electrons that flow in the same direction in a wire. (DC) n From batteries n Alternating current: electrons that flow in different directions in a wire. (AC) n From Generators n Used in your home n Transformers change AC to DC n

Measuring Electricity Current: Measured in Amperes or amps (A) n Voltage: Measured in volts (V) n Higher voltage, the more work the electrons can do. n

Measuring Electricity Resistance: the force opposing the flow of electrons. n Measured in ohms n Symbol is Greek letter omega n Thicker wire- less resistance n Longer wire- more resistance n Conductors- low resistance n Insulators- high resistance n

Ohm’s Law The relationship among current, voltage, and resistance. n Ohm’s law states that the current in a circuit is equal to the voltage divided by the resistance n. I=V R n V I R

Do the Math n. A car has a 12 volt system. The headlights are on a 10 amp circuit. How much resistance do they have? n Your house uses 120 volts. What amount of current would flow through a 20 ohm resistor?

Electric power and energy Power: The rate at which electricity does work or provides energy The amount of electric power a device uses to do work is determined by its resistance. n P= Vx. I n (P) power = (V) voltage x (I) current in the circuit. n

Formula for energy n. E=Pxt n (E) energy used = (P) power x (t) time n The SI unit for energy is a joule. n Kilowatt-hour meters measure the electricity used in your home. n (k. Wh) n