Electricity and Magnetism CRCT review

just like gravity A force that depends on: Size (mass or charge of objects) Distance between the centers

What particle? carries positive charge in the atom? Where is it? carries negative charge in the atom? Where is it? has no charge in the atom? Where is it?

static electricity Electric charges are separated. More of either protons or electrons in one place. How? Move electrons

Ways to move electrons friction – rub them from one object to another conduction – electrons flow from touching objects induction – electrons move in response to electric field without objects touching

Electric current What is electric current? What does an electric current cause? What is caused when the current is changing?

magnets Electrons with same spin line up and create magnetic domains. Permanent magnets: lots of aligned domains Cobalt, nickel and iron make good permanent magnets.

magnetic properties Always has both north and south pole Cut in half = two whole magnets

Earth’s magnetic poles hbase/magnetic/imgmag/mearthbar.gif

solenoid Coil of wire

electromagnet solenoid wrapped around an iron core The magnetic field inside iron magnifies the solenoid’s field

Stronger electromagnet More loops More current

Works other way too! Move the magnet to get an electric current. (Section 3) /73/ CDB7E548.gif

Electric motor An alternating current causes a magnet to spin The magnet is attached to some mechanical device that spins (ex: fan blade)

Electric generator A spinning magnet causes an alternating current.

Circuits energy source load wires

Circuits series lined up like train cars one current path same current everywhere parallel branches more than one current path same voltage on each branch

Schematic of a DC circuit with three resistor in series

Schematic of a DC circuit with three resistor in parallel

V = IR What happens to current if voltage increases? What happens to current if resistance increases?

SI units electric potential (aka: voltage) = volt (V) current = ampere (A) resistance = ohm (Ω)

Decrease resistance in a wire shorter wire thicker wire cool the wire