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physics test 3
Terms in this set (44)
Same for an electrically neutral atom
How does the number of protons in the atomic nucleus normally compare with the number of electrons that orbit the nucleus?
Positive charge since there will now be more protons as compared to electrons
What kind of charge does an object acquire when electrons are stripped from it?
A given amount of charge exists in the universe. You can not create or destroy charge only transfer it from one system to another.
What is meant by saying that charge is conserved?
decreases by a factor of ¼
How does the magnitude of electrical force between a pair of charged particles change when the particles are moved twice as far apart?
What condition is necessary for a sustained flow of electrical charge through a conducting medium?
Protons can not be removed from the nucleus but electrons can break free from the atomic shells and move around
Why do electrons, rather than protons, make up the flow of charge in a metal wire?
a current that flows in one direction
what is dc?
the current oscillates changing direction as well as magnitude
what is ac?
When the voltage is doubled the current doubles.
What is the effect on current through a circuit of steady resistance when the voltage is doubled?
are voltage and resistance proportional or inversely proportional ?
are voltage and current proportional or inversely proportional ?
The second lamp also has a current of 1 A since components in series all have the same current.
In a circuit consisting of two lamps connected in series, if the current in one lamp is 1 A, what is the current in the other lamp?
are resistance and current proportional or inversely proportional ?
the voltage of the second bulb would have to be 4 V in order to get 6 V total between the bulbs.
If 6 V were impressed across the circuit and the voltage across the first lamp were 2 V, what would be the voltage across the second lamp?
The voltage across the second lamp would have to also be 6 V since the voltage across all components in parallel is the same.
In a circuit consisting of two laps connected in parallel, if there is 6 V across one lamp, what is the voltage across the other lamp?
If both branches of a parallel circuit have the same current this means that they both have the same resistance.
If the current though each of the two branches of a parallel circuit is the same, what does this tell you about the resistance of the two branches?
The total current through the branches of a parallel circuit must add together to be equal to the current that comes out of the voltage source.
How does the total current through the branches of a parallel circuit compare with the current through the voltage source?
The bulb gets brighter.
What happens to the brightness of light emitted by a light bulb when the current that flows in it increases?
it will always be equal
Does more current flow out of a battery than into it?
The current will be larger when the bulb is connect to a 220 V source since voltage and current are proportional.
Will the current in a light bulb connected to a 220-V source be greater or less than that in the same bulb when it is connected to a 110-V source?
The higher wattage bulbs has more current flowing through and thus it has less resistance. wattage and resistance are inversely related
A car's headlights dissipate 40 W on low beam and 50 W on high beam Is there more or less resistance in the high beam filament?
series because as more bulbs are connected in series the overall resistance in the circuit increases.
to increase resistance in a circuit, should you connect them in series or in parallel? (think of toll analogy)
Parallel. As more bulbs are connected in parallel the overall resistance in the circuit decreases.
to decrease resistance in a circuit, should you connect them in series or in parallel? (think of toll analogy)
They will glow brighter if they are connected in parallel since each bulb will get the voltage of the battery and draw more current.
will a pair of flashlight bulbs glow brighter if they are connected in series or in parallel?
The battery will run down faster if the bulbs are connected in parallel. More power is being used over time (since they are brighter)
Will the battery run down faster if they are connected in a series or parallel?
As more bulbs are connected in series to a flashlight battery, the brightness of the bulbs decreases
As more and more bulbs are connected in series to a flash light battery, what happens to the brightness of each bulb?
When more bulbs are connected in parallel the brightness of the bulbs stays the same.
As more and more bulbs are connected in parallel to a flash light battery, what happens to the brightness of each bulb?
Permanent magnetics and current carrying wires both produce magnetic fields.
What produces a magnetic field?
orbit the nucleus and magnetic spin
What two kinds of motion are exhibited by electrons in an atom?
A region of space in a magnetic material
What is a magnetic domain?
Concentric circles centered on the wire and going around the wire
What is the shape of a magnetic field about a current-carrying wire?
The magnetic field changes direction so that it is exactly in the opposite direction to what it was
What happens to the direction of the magnetic field about an electric current when the direction of the current is reversed?
The magnetic field increases
How is the strength of a magnetic field in a coilwith currentaffected when a piece of iron is place inside?
When the current carrying wire is perpendicular to the magnetic field, the force on the current carrying wire is the greatest.
What relative direction between a magnetic field and a current-carrying wire results in the greatest force on the wire?
Whenthe current carrying wire is parallel to the magnetic field the wire experiences zero force and thus it is the smallest.
What relative direction between a magnetic field and a current-carrying wire results in the smallest force?
The force is in the opposite direction
What happens to the direction of the force on a wire when the current in it is reversed?
- change the magnetic field
-rotate the wire
-change the area of the coil
What are the three ways in which voltage can be inducted in a wire?
A generator and electric motor are basically opposites of one another. In an electric motor, electricity (current) is the input and the output is mechanical energy
What is the basic difference between a generator and an electric motor?
no, a transformer can not create energy.
does a transformer boost electric energy?
steps up the voltage
Does a step-up transformer step up the voltage, the current, or the power?
The current wire must be oriented parallel to the magnetic field
When a current-carrying wire is placed in a strong magnetic field, no force acts on the wire. What orientation of the wire is likely?
A changing magnetic field is necessary to induced voltage (current) in a coil.
Why does a transformer require alternating voltage (current)?
The current behaves opposite the voltage so if the voltage in the primary coil becomes twice that as the primary, the current is reduced by 1/2 that of the primary.
How does the current in the secondary of a transformercompare with the current in the primary when the secondary voltage is twice the primary voltage?
Can an efficient transformer step up energy?
Can an efficient transformer step up energy?
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