Download Chapter 8 Test Review – Electricity and Magnetism

Chapter 8 Test Review – Electricity and Magnetism
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Know how charges attract and repel one another
o S-S = Repel, N-N = repel, S-N = attract
Explain how a simple electroscope works to detect static electricity
o When a positively charged object comes near the top, the electrons within the
electroscope are drawn up into the foil ball leaving the tin foil leave both positive. They
repel.
o When a negatively charged object comes near the top, the electrons with the
electroscope are pushed down into the tin foil leaves making them both negative. They
repel.
Define static electricity, current , voltage, resistance, electrical power
o Static electricity = build up of charge
o Current = flow of electrons/electric charges
o Voltage = the potential energy difference needed to get current flowing (the push)
o Resistance = opposition to the flow of current
o Electrical power = the rate at work is done within an electrical device
Know the units used to measure current, voltage, resistance, power
o Current = amps (amperes)
o Voltage = volts
o Resistance = ohms
o Power = watts
Define conductor/insulator – examples of each
o Conductor = any material that allows electricity to flow easily (examples = most anything
metal)
o Insulator = any material that does not allow the flow of electricity (examples = wood,
yarn, rubber, plastic, etc.)
Know Ohm’s Law and how to use it to calculate current, voltage and resistance (I = V/R where
I = current, V = voltage, R = resistance)
Know the equation for electrical power (P = I x V where P = power, I = current, V =
voltage)
Review your Electrical Power Practice worksheet (especially the back side)
Define circuit, closed circuit, open current
o Circuity = a pathway for electricity to flow
o Closed circuit = allows electricity to flow, no breaks
o Open circuit = somewhere there is a break within the circuit/electricity cannot flow
Know the difference between series and parallel circuits (draw each)
o Series = one pathway
o Parallel = multiple pathways
Know what happens when you don’t put batteries in the correct way in an appliance
(circuit)
o Electricity cannot flow, the appliance does not work
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Be able to determine which bulb or buzzer would turn on if various switches were
opened or closed (circuit worksheet)
Define permanent magnet, electromagnet – advantages/disadvantages
o Permanent magnet = maintains magnetic properties all the time, cannot turn off
o Electromagnet = coil, current, core = can turn them on an off, can make them stronger
and weaker
Know what things can destroy a magnet
o Heating it up (melting)/dropping in many, many times
Know what happens when you cut a magnet in half
o You two new magnets, each with their own N and S poles
Be able to figure out which end of a magnet is N/S given several factors (i.e. compasses
around it/one known end)
Know how to calculate the strength of an electromagnet (ampere-turns) and how you can
change the strength (specifically) of an electromagnet – review your electromagnet
worksheet/science starters
o To determine the strength of an electromagnet, you multiple the current (amps) and
the number of turns
o Unit for strength of an electromagnet = amp-turns
o To increase strength, you either increase the number of turns or you increase the
current (amps)
Know how Earth’s magnetic field is aligned (geographic N/S vs magnetic N/S)
o Earth’s magnetic north pole is under the geographic south pole)
Know what a magnetic field is/looks like
NOTE: Read all of chapter 8, and be able to answer the chapter review questions at the end of the
chapter