41 terms

Physics Circuits

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Electric Potential Energy (3/4ish components)
Energy of a charge based on its location in an electric force field. Like charges: closer together, more EPE. Unlike charges: farther away, more EPE. More work required to push charged particle against electric field of charged object increases EPE
Electric Potential
Electric Potential energy per charge
Voltage
Electric Potential energy per charge. Does not "move" - only charges can. "Pushes" the electricity through the circuit - causes it to flow.
electromotive force (EMF)
Electric Potential energy per charge. Also known as the force that moves charge
Uniform Field
Electric field where field lines are parallel. Entering electrons move in a parabola towards the positive side. Entering protons do the opposite.
Electricity
The flow of electric charge from a high potential to a low potential
What two things are required to make current flow?
1. a difference in electric potential (at either end)
2. a closed path of conducting material
How do charges move?
From areas of high charge to low charge
Conductor
allows electricity to flow easily
Insulator
does not allow electricity to flow easily
Current
The net flow of electrons through a conductor/The number of electrons that pass a specific point in a circuit in one second. Meaured in amps. Is a rate.
Conventional current
the way current is traditionally said to flow through a circuit: from positive to negative
How does current actually flow in a circuit?
From negative to positive
Direct (DC) Current
current in a circuit that flows in only one direction. Positive and negative ends are fixed, flow is from positive to negative. Example=batteries
Alternating (AC) Current
Current in a circuit that oscillates back and forth. Positive and negative ends switch back and forth so current's direction switches back and forth. Example=power plant, wall socket
Circuit
closed path in which a current can flow between a difference in potential
Wire
Part of a circuit. Connect different components in circuits. Are very good conductors. 2 types - braided v. stranded
Resistors
Part of a circuit. Doesn't allow for flow of charge freely, slows down flow of charge. Reduces danger and protects equipment.
Lightbulb
Example of resistor. A glass container that contains a coiled wire surrounded by a vacuum.
Power sources
Part of a circuit. Supply the potential difference in a circuit, are the reason why charges flow: they supply energy. Two types - DC and AC
Capacitors
Part of a circuit. A device used for storing electric potential energy. Two conductors separated by an insulator - when the latter is removed, electrons jump. So, they store charge but also release it quickly. Most simply is a set of oppositely charged plates, with a magnetic field between where EPE is stored. Examples are switches (allow circuits to close.turn on and open/turn off).
Diode
Part of a circuit. Allow charge to flow in only one direction. Examples - LED
What 2 things does the amount of current flowing through a circuit rely on?
1. resistance
2. voltage
Resistance
degree of opposition (friction) that charges encounter as they move through a conductor. Measured in Ohms. Is a characteristic of a wire.
4 things that affect resistance
1. length
2. thickness
3. temperature
4. material
Ohm's Law
Current = voltage/resistance. Shows relationship between the 3 variables. Basically, more resistance means less current.
Power Law
Power = current*voltage. Shows relationship between power, current, and voltage.
Power
Rate at which work is done/energy is used
Types of circuits
Series circuit and parallel circuit
Series Circuit
Connected such that current only has one path to pass through. If one thing stops working, everything stops working
Parallel Circuit
Connected such that current has multiple paths to pass through. If one thing stops working, others things may remain working
Voltage Drop
the portion of the total voltage in a (series) circuit used up by a resisting component
Series Circuit Rule: Voltage
The total voltage is equal to the sum of the voltage drop across each resistor: Vt=V1+V2...+Vn
Series Circuit Rule: Current
The current does not change as it flows through the circuit: It=I1=I2=...In
Series Circuit Rule: Resistance
The EQUIVALENT (total) resistance is equl to the sum of the individual resistors: Req=R1+R2+...Rn
Parallel Circuit Rule: Voltage
The voltage through each branch is the same: each branch needs to use up the available voltage: Vt=V1=V2=V3
Parallel Circuit Rule: Current
The total current is equal to the sum of the currents through each branch of the circuit: It=I1+I2+...In
Parallel Circuit Rule: Resistance
The inverse of the EQUIVALENT resistance is equal to the sum of the inverse of the individual resistors:
1/Req=1/R1+1/R2+...1/R3 or
Req=(1/R1+1/R2+...1/R3)^-1
Fuses
A device, in series with many parallel branches, that breaks when too many resistors are added in parallel and the total resistance becomes too low, causing the current to be too high
Capacitance
C=Q/changeinV
Physical property that dictates amount of charge required to be stored to attain certain amount of potential difference between plates
Short Circuit
A special type of circuit, usually caused when electricity is allowed to travel through an unintended path. Can cause circuits and appliances to break, heat wires enough to start a fire. Danger comes from too high current in wire.