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111 terms

Physics Test: Current Electricity and Circuits

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The rate of flow of electric charges
current
What is the symbol for current? Unit?
I, Amperes (A)
In a current, how do charges move?
Randomly
Electric currents when connected to a potential difference, it creates a(n) _ field which creates a(n) _ force setting _ in motion
electric, electrical, charges
What do batteries and generators have to do to charge carriers?
work/supply energy
What do batteries and generators set up across a circuit?
a potential difference
Batteries convert what to what?
chemical PE to electrical PE
Generators convert what to what?
mechanical energy to electrical PE
Do batteries and generators give the circuit charges?
no
Since batteries and generators don't give the circuit charges, the just...
force the charges to move in one direction *note, the electrons are already on the wire
Electrons flow from (positive/negative) to (positive/negative)
negative to positive
The electrical force _ the electrons to/from the positive terminal and the electrons are _ to/by the negative terminal
attracts, repelled
Electrons move from an area of (high/low) electric potential to an area of (high/low) electric potential (AKA voltage)
high, low
How does the flow of current in batteries work?
The negative terminal loses negative charge and eventually becomes positive. The positive terminal gains negative charge and eventually becomes neutral. Once the charges even out, there is no longer a potential difference between them, and the flow of electrons (current) stops
The direction that positive charges would flow (if they did flow)
conventional current, positive to negative
Which way does conventional current flow?
from positive to negative
The direction that electrons (negative charges) would flow
Actual current, negative to positive
Which way does actual current flow?
from negative to positive
Do you know how to draw pictures of both conventional flow notation and electron/actual flow notation?
yes
The opposition to the flow of current in a conductor
Resistance
The higher the resistance, the _ current can make it through
less
What is the symbol for resistance? Unit?
R, Ohms (Ω)
Put in a circuit to control (slow) the flow of current
resistor
Materials that have a resistance of zero
superconductors
What are the three factors affecting resistance?
length, cross-sectional area, and conductivity
Longer length = _ resistance, shorter length = _ resistance
more, less
What is another name for cross-sectional area?
thickness
The smaller the area (or thinner) = _ resistance, the larger the area (or thicker) = _ resistance
more, less
What is another way to explain conductivity?
the type of material used
Higher conductivity = _ resistance, lower conductivity = _ resistance
low, high
For most conductors, the amount of resistance remains constant. This is...
Ohm's law
The amount of current that flows through a circuit is _ly proportional to the voltage supplied to the source
directly
The amount of current that flows through the circuit is _ly proportional to the resistance of the conductor
inversly
The rate at which energy is converted from one form to another
power
What is the derived power formula that you are not given?
P=I^2R
What is the derived energy formula that you are not given?
E=ΔVIT
What is the symbol for power? Unit?
P, Watts (W)
Power times time
Energy
What is the symbol for energy? Unit?
E, Joules (J)
Energy per unit of time
power
Does a high powered light bulb put out a lot or a little of light per second?
a lot
One joule per second is also known as a...
watt
One coulomb per second is also known as a...
amp
When you multiply voltage times current, you get _
power
In a 120 volt electrical outlet, every Coulomb of charge does _ Joules worth of work as it moves from one side of the outlet to the other
120
The ability of a conductor to store energy in the form of electric charge
Capacitance
What is capacitance measured in?
Farad
Pico is...
-12
Micro is...
-6
An electrical device that stores electrical charge and energy which can be removed for use at a later time
Capacitor
Two conductors, separated by an insultar. Acts as a storehouse of charge that can be reclaimed when needed
capacitor
Used in electronic devices to maintain power supply while batteries are being charged, prevents memory loss
capacitor
Thing where plates are connected to a potential difference (voltage source) such as a _
parallel-plate capacitor, battery
How do parallel-plate capacitors work?
charge is removed from one plate and collects on the opposite plate
When do charge transfers stop in parallel-plate capacitors?
when the potential difference of the plates equals the potential difference of the battery it's connected to
How is discharging done in a parallel-plate capacitor?
by connected the capacitor to a conductor via a switch (ex. flash of a camera)
All schematic diagrams are drawn using which current?
conventional
What condition is necessary for the flow of heat? What analogous condition is necessary for the flow of charge?
temp difference, potential difference
What is meant by potential difference? What does a potential difference produce in a circuit?
voltage, current
What conditions are necessary for the sustained flow of water in a pipe? What analogous condition is necessary for the sustained flow of charge in a wire?
pressure difference, potential difference
What is electric current?
flow of charge/moving of electrons
What is an ampere?
unit of current (1 C/s)
What is a volt?
potential difference (1 J/C)
How many joules per coulomb are given to charges that flow in a 120-volt circuit?
120 v
Does charge flow through a circuit or into a circuit?
through (electrons already on wire)
Does voltage flow through a circuit, or is voltage established across a circuit?
established across
What is electrical resistance?
resists current
If the voltage impressed across a circuit is constant but the resistance doubles, what change occurs in the current?
cut in half (inverse)
If the resistance of a circuit remains constant while the voltage across the circuit decreases to half its former value, what change occurs in the current?
cut in half (direct)
How does wetness affect the resistance of your body?
resistance decreases
Distinguish between AC and DC. Which is produced by a battery and which is usually produced by a generator?
alternating current in generators or outlets (2 way), direct current in batteries (1 way)
From where do electrons originate that flow in a typical electric circuit?
on the wires or conductors
What is power?
the rate of doing work (1 Watt = 1 J/s)
Drawings that represent electric circuits using standards symbols for circuit elements
schematic diagrams
A complete path (loop) which charge can flow
circuit
What are 3 things found in a common circuit?
voltage source (battery, generator, etc), conductor (wire), device to receive electrical energy (light bulb)
In a common circuit electrons flow from _ to _
negative to positive
For a continuous flow of electrons, the circuit must be _ with no _
complete, gaps
What will happen if there is a break in an electric circuit?
here will be a complete stop in the flow of electrons
What is an example of something that can be used to break a circuit?
a switch
Electric current that repeatedly reverses in direction, twice each cycle. Usually at 60 cycles per second
Alternating current
Example(s) of alternating current
generator, outlet
"Two way street"
alternating current
Electric current whose flow of charge is always in one direction
Direct current
"One way street"
direct current
Example(s) of direct current
batteries
What is the primary use of current?
to transfer electrical energy
Which type of circuit allows current to travel great distances with easy voltage step-ups that result in lower heat losses in wire?
AC circuits
What 2 things can be inserted into lines that provide power to prevent overloading?
fuses and circuit breakers
What will excessive current do to the fuse, circuit breaker, and circuit?
blow out the fuse, trip the circuit breaker, and provide a break in the circuit
Resistors are connected such that there is a single pathway for electron flow
series circuit
In a series circuit, what stays the same?
current
What is the formula for the total current in a series circuit?
Vt=ItRt
How do you find the voltage drop across each device in the series circuit?
V1=ItR1 (V2=ItR2, etc)
According to _ Law, in a series circuit there is a voltage drop across each device that depends directly on its _
Ohm's, resistance
Formula for the total voltage in a series circuit
Vt=V1+V2+V3...
In a series circuit, _ is the same throughout each resistor
current
In a series circuit, _ is different through each resistor
voltage
In a series circuit, the parts equal the whole for...
voltage
Resistors are connected such that there are multiple pathways for electrons to flow
parallel circuit
In a parallel circuit, what stays the same?
voltage
What is the formula for total current in parallel circuits?
Vt=ItRt
What do you notice about the series circuit formula for total current and the parallel circuit formula for total current?
same (Vt=ItRt)
What is the formula to find total current in a parallel circuit?
It=I1+I2+I3...
In a parallel circuit, _ is different through each branch (resistor)
current
In a parallel circuit, _ is the same through each branch (resistor)
voltage
In a parallel circuit, _ the parts equal the whole for...
current
Do you know how to find equivalent resistance?
yes
Do you know how to work with complex circuits?
yes
Current is proportional to resistance...
parallel
Voltage is proportional to resistance...
series