Topic 5.2: Electric Circuits Flashcards
Define electromotive force (emf)
o EMF (E): The total electrical energy given by the battery to each coulomb of charge OR the terminal potential difference of the source when no current flows
Define internal resistance
o Internal Resistance: The resistance of the battery. Some of the energy provided by the source is converted to heat here and is not available in the external circuit components.
Define terminal potential difference
o Terminal Potential Difference: The potential difference measured across the terminals of the source which is less than the emf due to the internal resistance of the source.
Describe resistors in parallel
Resistors in Parallel: Connected like a ladder. They all experience the same potential difference across them. 3 Facts to know:
The potential difference across each resistor in parallel is the same
The current in the main circuit is the sum of the currents in each of the parallel branches, so I= I_1+I_2+I_3+…
Describe resistors in series
Resistors in Series: Connected like a chain. They all have the same current flowing through them. 3 Facts to know:
The current through each resistor in the series is the same
The total potential difference, V, across the resistors is the sum of the potential differences across the separate resistors, so V=V_1+V_2+V_3+…
The combined resistance R in the circuit is the sum of the separate resistors
Define ammeter
o Ammeter: Instrument which measures current in a circuit. It must be connected in series with the current it measures and has a very low resistance.
Define voltmeter
o Voltmeter: Instrument which measures potential difference in a circuit. It must be connected in parallel with the potential difference it measures and has a very high resistance.
Define ideal meter
o Ideal Meters: These do not affect the readings they make. Ideal ammeters and voltmeters have zero and infinite resistances respectively.
Define potential divider
o Potential Divider: The potential divider of a source is divided over two resistors in series in proportion to their resistances
Define electrical sensor
o Electrical Sensors: A component whose electrical properties (usually resistance) changes with its physical conditions.
Define thermistor
o Thermistor: A resistor whose resistance falls when its temperature rises.
Define light dependent resistor
o Light Dependent Resistor: A resistor whose resistance falls as the intensity of light falling on it increases
Define strain gauge
o Strain Gauge: A long thin wire whose resistance increases when it is stretched.
Define potential divider
o Potential Divider: The potential divider of a source is divided over two resistors in series in proportion to their resistances.
Define sensor circuits
o Sensor Circuits: One of the resistors in a potential divider is replaced by a sensor so that the potential divider across the resistors in the potential divider changes as a physical condition changes (eg temperature, light intensity or strain).
