Glossary
Ammeter
A device used to measure the electric current flowing through a specific point in a circuit.
Example:
To find out how much current is flowing through a light bulb, you would connect an ammeter in series with it.
Electromotive Force (ε)
The maximum potential difference a battery or power source can provide when no current is flowing through it; its ideal voltage.
Example:
A 9V battery has an electromotive force of 9 volts, which is its voltage when nothing is connected to it.
Equivalent Resistance (R_eq)
A single effective resistance that can replace a group of resistors in a circuit, simplifying analysis.
Example:
When analyzing a complex circuit with multiple resistors, calculating the equivalent resistance allows you to treat the entire network as a single resistor for initial current calculations.
Ideal Ammeter
A theoretical ammeter with zero internal resistance, ensuring it does not affect the current it is measuring in a circuit.
Example:
In circuit diagrams, we often assume an ideal ammeter to simplify calculations, knowing it won't alter the circuit's current.
Ideal Components
Theoretical circuit elements assumed to have perfect characteristics, such as wires with zero resistance or batteries with no internal resistance.
Example:
For initial circuit analysis, we often assume wires are ideal components with no resistance to simplify calculations.
Ideal Voltmeter
A theoretical voltmeter with infinite internal resistance, ensuring it draws no current and accurately measures the potential difference without altering the circuit.
Example:
When designing a perfect measurement setup, engineers aim for an ideal voltmeter that won't load the circuit being measured.
Internal Resistance (r)
The inherent resistance within a real battery or power source that causes a voltage drop when current is drawn from it.
Example:
A worn-out car battery might have a high internal resistance, leading to a significant voltage drop when trying to start the engine.
Nonideal Ammeter
A real ammeter that possesses a small, but non-zero, internal resistance, which can slightly reduce the current in the circuit it measures.
Example:
Using a nonideal ammeter in a very low-resistance circuit might lead to a slightly lower current reading than the actual current without the meter.
Nonideal Battery
A battery that behaves like an ideal voltage source in series with a small internal resistance, causing its terminal voltage to drop when current flows.
Example:
When you turn on your car, the headlights might dim slightly because the starter motor draws a large current, revealing the nonideal battery behavior.
Nonideal Voltmeter
A real voltmeter that has a very high, but finite, internal resistance, causing it to draw a small amount of current and potentially alter the voltage it measures.
Example:
If you use a nonideal voltmeter to measure voltage across a very high-resistance component, the voltmeter itself might draw enough current to slightly change the voltage you're trying to measure.
Parallel Connection
A circuit configuration where components are connected across the same two points, providing multiple paths for current flow.
Example:
The outlets in your house are wired in a parallel connection, so if you unplug one appliance, the others continue to work.
Parallel Resistors (Calculation)
The method for calculating the equivalent resistance of resistors connected in parallel using the reciprocal of the sum of their individual reciprocals.
Example:
Two 10 Ω resistors connected in parallel have a parallel resistors equivalent of 5 Ω, calculated as 1/(1/10 + 1/10).
Real-World Components
Actual circuit elements that possess non-ideal characteristics, such as wires having some resistance or batteries having internal resistance.
Example:
A long extension cord is a real-world component that will have a measurable resistance, unlike an ideal wire.
Series Connection
A circuit configuration where components are connected end-to-end, forming a single path for current flow.
Example:
In a string of old Christmas lights, if one bulb burns out, the entire string goes dark because they are in a series connection.
Series Resistors (Calculation)
The method for calculating the equivalent resistance of resistors connected in series by simply adding their individual resistances.
Example:
If you have 5 Ω and 10 Ω resistors in series, their series resistors equivalent is 15 Ω.
Terminal Voltage (ΔV_terminal)
The actual voltage measured across the terminals of a real battery when current is flowing, which is less than its EMF due to the internal resistance.
Example:
A 12V car battery might only show an 11V terminal voltage when the engine is cranking, due to the current drawn and its internal resistance.
Voltmeter
A device used to measure the potential difference (voltage) between two points in a circuit.
Example:
To check the voltage supplied to a resistor, you would connect a voltmeter in parallel across its terminals.