Chapter 8.9 Electric Circuits
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What is a circuit?
Any path along which electrons can flow
What must there be fore a continuous flow of electrons?
There must be a Complete Circuit with No Gaps
What usually constitutes a gap in electrical circuits?
An electric switch that can be opened or closed to either cut off energy or allow energy to flow
In what two ways are devices commonly connected in a circuit?
In Series or in Parallel
How are devices connected in a Series?
They form a single pathway for electron flow between the terminals of the battery, generator, or wall outlet
How are devices connected in Parallel?
They form branches, each of which is a separate path for the flow of electrons
Does the current pile up or accumulate in any of the three lamps in a simple circuit?
No it flows through each lamp almost immediately in each
What would happen if there was a break anywhere in the path of the electrons? (Switch opening)
It would be an open circuit, and the flow of electrons would cease
In a series circuit, is the current passing through each electrical device the same or different?
It is the same because electric current has a single pathway through the circuit
In a series circuit, how do you find the total resistance to current in a circuit?
You add the resistance of all the individual devices to find the sum of the individual resistances along the circuit path.
Is the total voltage impressed across a series divided among the individual electrical devices?
Yes The sum of the voltage drops across the resistance of each individual device is equal to the total voltage supplied by the source
The sum of energies given to each device is equal to what?
The amount of energy given to the total current
What is the voltage drop across each device proportional to?
The voltage drop across each device is proportional to its resistance
What happens to the brightness of each lamp in a series circuit when more lamps are added to the circuit?
This produces a greater circuit resistance. This decreases the current in the circuit and therefore in each lamp, which causes the dimming of the lamps. Energy is divided among more lamps, so the voltage drops across each lamp is less.
What is Voltage Drop?
The amount of voltage loss that occurs through all or part of a circuit due to impedance
What is the main disadvantage of a series circuit?
If one device fails, current in the entire circuit ceases
In a parallel circuit, is the voltage the same across each device?
Yes
In a parallel circuit, does the current divide among the parallel branches?
Yes Because the voltage across each branch is the same, the amount of current in each branch is inversely proportional
The amount of current in each branch is inversely proportional to what?
The resistance of the branch
What is the sum of the currents through each of the parallel branches equal to?
The sum of the current in each parallel branch is equal to the original current through the voltage source
When you add a parallel branch, is overall resistance increased or decreased?
Overall resistance is lowered with each added path between any two points of the circuit
Is the overall resistance of the parallel circuit greater than or less than the resistance of any one of the branches?
It is less than
In a parallel circuit, what happens to the current in the other lamps if one of the lamps in a parallel circuit burns out?
If one burns out, the others are unaffected. Because neither voltage nor resistance (Ohm’s law) is affected in the other branches, the current in those branches is unaffected.
In a parallel circuit, what happens to the brightness of each lamp when more lamps are added in parallel to the circuit?
The brightness of each lamp is unchanged as other lamps are introduced (or removed). Only the total resistance and total current in the total circuit changes, which means that the current in the battery changes.