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13 terms

PHYS 101 - 2 - Circuits : Direct and Alternating Current

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Electric Current
It is the flow of electrons through a conductor.
Direct Current
Electrons made to flow in one direction only.
Alternating Current
It is the current in which electrons oscilate back and forth. It is required in most applications.
Series Circuit
Parallel Circuit
What are the two principal types of Electrical Circuits?
Series Circuit
A circuit in which the current has only one path to travel. All component parts are connected end to end.
A break anywhere in the path results in an open circuit and the flow of electrons ceases.
1.) The total resistance is equal to the sum of the individual resistances along the path.

2.) Current through each circuit element is the same and is equal to the total circuit current.

3.) The sum of the voltages across each resistor is equal to the total circuit voltage.
What are the characteristics of a Series Circuit?
Parallel Circuit
A circuit in which there are more than one path for the current to flow. The components are branches of the main circuit. A break in any one path does not interrupt the flow of charge in the other paths. A break in any one path does not interrupt the flow of charge in the other paths.
1.) Sum of the current through each circuit element is equal to total circuit current.

2.) Voltage across each circuit element is the same and is equal to the total circuit voltage.

3.) Current flows more readily into devices of low resistance, so the amount of current in each branch is inversely proportional to the resistance of the branch.

4.) Total resistance is inversely proportional to the sum of the reciprocals of each individual resistance

5.) As more resistors are added in parallel there is an increase in their total cross-sectional area so that the total resistance decreases.
What are the characteristics of a Parallel Circuit?
1.) Total resistance is equal to the sum of the separate resistances.
RT = R1 + R2 + R3

2.) Current in the circuit is the same everywhere in the circuit.
IT = I1 = I2 = I3

3.) The sum of the voltage drops must add up to the EMF or voltage of the source.
VT = V1 + V2 + V3

4.) Total power is the sum of the power consumed
or dissipated by each resistor or load.
PT = P1 + P2 + P3
The Ohm's Law applied to a series circuit?
Voltage Drop (IR Drop)
It is the amount of potential difference across a resistor. This is the amount of voltage required to push a specific amount of current across a resistor. It indicates that there is a "fall" or "drop" in potential across a resistor, and as the resistance increases so does the potential drop. The sum of the voltage drops must add up to the EMF or voltage of the source.
P = I x V
What is the formula for power? (Watts)
Pt = It x Vt
The total power consumed by the entire circuit may be found by multiplying the voltage of the source by total current. What is the formula?
1.) The total resistance is always less than the lowest valued resistor.
1/Rt = 1/R1 + 1/R2 + 1/R3

2.) The total current will equal the sum of the current in each branch.
IT = I1 + I2 + I3

3.) The voltage is the same in all branches of the circuit.
VT = V1 = V2 = V3

4.) The total power is the sum of all the power consumed in each branch.
PT = P1 + P2 + P3
The Ohm's Law applied to a parallel circuit?