Electricity and Magnetism
What is the law of conservation of charge?
Charge cannot be created or destroyed - only transferred from one object to another
What are the two different ways of transferring electrical charge?
Charging by induction (over a distance), Charging by contact touching.
Give 2 examples each of a good electrical conductor and a good electrical insulator
Conductors: metal, water Insulators: plastic, rubber
Which type of current does not reverse direction?
Direct - DC
Why would a compass' needle turn if placed next to an electric outlet?
Electric current produces a magnetic field and mess up the magnetic needle.
The kilowatt-hour is the unit of what?
Electrical Energy
An electric motor changes ________________ energy into ______________ energy?
Electrical, mechanical
Write the equation for finding the amount of electrical energy if you know how much power a device uses and the time it has been running?
Energy = power x time
What is a magnetic domain?
Groups of atoms with aligned magnetic poles
Electrons travel from areas of ______ voltage to areas of _______ voltage
High, Low
What does a transformer do and why is it helpful?
It increases or decreases the voltage flowing through it
What are the two coils of wire in a transformer called?
Primary and secondary
Why does current usually involve the flow of electrons but not the flow of protons?
Protons are locked deep within the center of atoms and do not move, but the outer, loosely held electrons are free to move.
How could you tell quickly if a string of lights is wired in series or parallel?
Remove one bulb. If it's a series, all the lights will go out; if it's parallel, the remaining lights will stay lit.
What is resistance? What is the unit of resistance?
Resistance is the tendency of an object to prevent the flow of current, the unit is the "ohm" (Ω)
Draw a series circuit and parallel circuit. Be sure you understand the difference between the two and can recognize them when you see them.
See Notes
What is electrical charge that has accumulated on an object called?
Static electricity
A transformer that increases voltage is what type of transformer?
Step-up transformer
What happens to the magnetic domains in a temporary magnet when it is placed in a strong magnetic field?
The Domains become aligned
What is electrical current and what are the units of current?
The flow of electrons through a wire or any conductor
If magnets are placed next to each other with their north poles facing each other, what will happen to the magnets?
They will repel
What do two objects do when they are both positively charged?
They will repel each other
What is ohms law? Be sure to identify the different parts and be able to solve a problem.
Voltage = Current x resistance
What are common sources of AC power? What are common sources of DC power?
Wall Socket: AC Battery- DC
What is the unit of electrical power?
Watt
What is the definition of electromagnetic induction?
When you cause an object to be charged without touching the object using electricity
Why is a circuit breaker important in a household electrical system?
1. A circuit breaker prevents too much charge from passing through the house's wires which might cause a fire or shock
What voltage does the transformer outside of your house convert the current to for use in your home?
120 volt alternating current - it is a step down transformer
What is lightning and why does it occur?
4.Lightning is a large discharge of static electricity caused by an unbalanced charge between the cloud and the ground.
If a magnet with two poles is cut in half, how many poles will now exist between the two magnets?
4: There will be 2 north and 2 south
What is the difference between a dry cell and wet cell battery?
A dry cell battery contains the reactions within a moist paste - most household batteries are dry cell. A wet cell battery requires some conductive battery solution. An example of a wet cell would be a car's battery
Which type of current constantly changes direction?
Alternating - AC
Why do clothes stick together after they have been put through a drier?
As the clothes rub against each other, some clothes lose electrons to become positively charged. Others gain electrons to become negatively charged. The opposite charges attract.
How does rubbing a balloon against your hair create static electricity?
As you rub the balloon against your hair, the electrons are rearranged to cause a difference in charge. This is known as charging by induction.
Where in the magnetic field surrounding a bar magnet is the magnetic field the strongest?
At the poles
Why do electrical wires have a plastic coating wrapped around them?
Because plastic is a good insulator
The region around a magnet where the magnetic forces act is the...?
Magnetic Field
A dam converts _______________ energy from the falling water into _____________ energy
Mechanical, Electrical
A generator changes ______________ energy into ______________ energy?
Mechanical, electrical
Does an electrically neutral atom have more electrons or protons?
More electrons than protons
What type of circuit exists in a string of Christmas lights? How do you know this?
Parallel circuit, if one bulb burns out, the rest of the lights stay on
