Introduction to Electric Current Electric Current The continuous

Introduction to Electric Current

Electric Current The continuous flow of electric charge Flows when there is a potential difference (V) between two points To create the difference, work must be done on the charges by a charge pump

Charge Pumps Photocell (solar cell) - converts light energy into electricity Ex: Calculators and street lights Battery (voltaic or electrochemical cell) converts chemical energy into electricity Fuel cells added chemical reactants to keep the reaction going Generator - converts mechanical energy into electricity

Generators Electricity and magnetism are two sides of the same electromagnetic force. Generators move a coil of wire (mechanical energy) inside of a magnetic field to create current.

Hand Crank Generators 1. Attach the two leads to the ends of the bulb holder. 2. Crank to light the bulb. What happens to the brightness as you crank faster? 3. Disconnect the cable to the light. Crank again. What was the difference and why? 4. Connect the lead and crank slow and steady to light the bulb. Have a partner disconnect the bulb as you continue to crank. What happened? Why?

Electric circuit Complete conducting path through which electrons flow. For current to flow, the circuit must include Closed path Charge pump (Voltage source)

conductor closed switch open switch load battery fuse resistor

Load Device that uses electrical energy Work is done on/by the electrons and their potential energy increases/decreases. Since it opposes the flow of current, a load is a type of resistor. Does not have to be a light bulb Can be a buzzer, motor, or heating element

Draw the schematic diagram for the following

Fact or Fiction? When you turn on a light switch, electrons move rapidly from the to the lamp to the light bulb.

Heat is always a side-effect of electric current. Due to electron drift. Electron drift causes the electrons to move so slow, it would take them 1 hour to move a meter.

How does the bulb light immediately when the switch is closed? All the devices already have electrons in them. When you close the switch the electrons all begin to move at the same time. Having a potential difference between two points in a circuit sets up an electric field through the conductor, which moves at the speed of light, setting electrons in motion.

Current Direct current (dc) - electrons move in one direction Alternating current (ac) - electrons change directions - In the USA, direction changes 60 times per second

Conventional Current Conventional current flows opposite the way an electron would flow. Positive to negative. Based off of electric fields, which state how a positive charge would move in the field.