CFI Physics Final Review


According to the law of conservation of electric charge you can't create a _______ charge without also creating a _______ charge.


positive; negative


Electric field lines _______ from positive charges.


point away


A positive and negative charge will ______ each other.


attract


How many joules of energy will a 12-volt battery add to each coulomb of charge?


12


When you comb your hair, what does the comb become?


Negative because electrons are transferred to it from your hair


Which of the following is a would be a poor conduction:
Copper
Salt Water
Graphite
Plastic


Plastic


What is the SI unit of an electric charge?


Coulomb


Electric charges exist only in whole number multiples of the _______.


Electron charge


What will a charge moving along an equipotential have?


No change in electric potential energy


You have built an enormous Van De Graaf generator - so large that the control room fits inside the dome. Is this a safe place to be?


Yes, because ther eis never a charge inside a charged conductor


What is the potential difference expressed in volts?


Coulombs of charg flowing per second


If two charge are 1mm apart and you increase the distance between them to 4mm, ther force between them will ______ as strong.


1/16


If you know the magnitude of the negative charge on an object, what can you calcuate?


total number of electrons


What is the valid expression on Ohm's Law?


V=IR


A Nb-Sn alloy has no electrical resistance at 28 K. This alloy would be considered to be a _____________.


superconductor


What type of circuit are typical household electric circuits?


Parallel circuits


Three devices are connected in a series circuit. Device A has a resistance of 6ohms; Device B 20ohms; Device C 24ohms. What is the toal resistance in the circuit? What if it is a parallel circuit?


50ohms (Series)3.9 (Parallel)


Which of the following units is actually a measure of a rate?


Amp


Ther resistance in a current-carrying wire depends upon what properties?


The length of the wire, thickness of the wire, and the resistivity of the metal


Doubling the cross-secitonal rea of a wire reduces resistance by how much?


0.25


Where would the terminal potential difference of a battery be less than it's emf?


Because of the internal resistance of the battery


What is the unit of emf?


Volt


What device would you use to measure the rate of flow of charge?


ammeter


How do batteries work?


By adding energy to exisiting charges


Which of the following materials would be suitable for a permanent magnet:
Nickel
Cobalt
Iron
Steel


True or False: Magnetic field lines from continous loops.
True False


True


What is the SI unit of a magnetic field?


Telsa (T) and/or Newton per Amp-meter


The force that a magnetic field exters on a current is _______ to the field.


Perpendicular


What law states that when a current in induced, it generates a field that opposes ther change that induced it?


Lenz's Law


Where is magnetic north located on Earth?


At the geographic north pole


If you cut a permanent bar magnet in half, what will you get?


2 magnets, each with a North and South Pole


The magnetic field surrounding a straight, current-carrying wire is _______.


a series of concentric circles


A magnetic field has no effect on a(n) ________.


Electric current


What is the product of magnetic field strength and the area of the loop called? What is it measured in?


Magnetic flux; webers


Define Electrostatic conduction.


The separation of charge produced when a conductor is moving in a magnetic field


Which of the following has the strongest magnetic field:
Giant particle accelerators
MRI machines
Earth
Refrigerator magnet


Giant Particle accelerators


What type of currents attract each other?


Parallel


What is the average value of an alternating current?


It is proportional to frequency


You decide to talke apart a transformer and find that the primary coil has 100 turns and the secondary coil has 20 turns. If the potential difference in the primary is 120 V, what will be the induced potential difference in the secondary coil? What type of transformer is this?


24 V; Step Down


A Weston galvonmeter can be converted in which types of meters?


Ammeter, voltmenter, and ohmeter


What is the function of the commutator in an electric motor?


to reverse the current in the armature every half cycle


Which of the following wires could safely carry the highest current:
#10, #12, #8, or #14


#8


How does a fuse interrupt a current and protects against circuit overload?


Melting when the current gets too high


Which color wire in an electric cable is connected to the grounding terminal?


Green


Homes in the US use 110 V AC. Why does the eelctric company transmit current at a potential of over 200,000 V?


To reduce power loss in the line


AC power is equal to ______.


I2R


What range does a Weston galvonometer measure currents in?


Ampere


What factors determine the rate at which a wire can give up heat?


Temperature of the wire, type and thickness of insulation, and the thickness of the wire