Electricity Flashcards
Definitions from Higher Physics unit 2
What is meant by a “Electrical conductor”?
A material that lets current flow easily through it.
What is meant by an “Electrical insulator”?
A material that does not let current flow easily through it.
What is meant by “Voltage”?
The amount of energy supplied to each coulomb of charge passing through the cell.
What is meant by “Electrical current”?
The amount of charge flowing past a point in one second.
What is meant by “Direct current”?
Electron flow in one direction from negative to positive.
What is meant by “Alternating current”?
The direction of electron flow changes back and forth many times a second.
What is the value of Mains voltage in the U.K.?
230 V
What is the frequency of Mains electricity in the U.K.?
50 Hz
What is the function of a Cell or Battery in an electrical circuit?
To provide electrical energy to the circuit.
What is the function of a Bulb or Lamp in an electrical circuit?
To convert electrical energy into light energy.
What is the function of a Motor in an electrical circuit?
To convert electrical energy into kinetic energy.
What is the function of an L.E.D. in an electrical circuit?
To convert electrical energy into light energy.
What does L.E.D. stand for?
Light Emitting Diode
What does L.D.R. stand for?
Light Dependant Resistor
What environmental factor affects an L.D.R.?
Light
What environmental factor affects a Thermistor?
Temperature
What does an Ammeter measure?
Electrical Current
What does a Voltmeter measure?
Voltage
What does an Ohmmeter measure?
Resistance
What is the function of a capacitor in an electrical circuit?
A device for storing electrical charge.
What is the function of a Transistor in an electrical circuit?
Voltage dependant switch
What is meant by a “Series” circuit?
Circuit with one path for the current to flow through.
What is meant by a “Parallel” circuit?
Circuit with two or more branching paths for the current to flow through.
What is meant by “Power”?
The energy used / transferred every second.
What is the rule for series voltage?
In a series circuit, the voltage across each component adds to the supply voltage.
What is the rule for series current?
In a series circuit, the current is the same at all points.
What is the rule for parallel voltage?
In a parallel circuit, the voltage across each branch is equal to the supply voltage.
What is the rule for parallel current?
In a parallel circuit, the current through each branch adds to the supply current.
What is the purpose of a resistor in series with an LED?
To protect the LED from too large a current.
What is meant by the “Internal resistance” of a cell?
The resistance due to the chemicals within the cell, a small amount of energy per coulomb will be lost moving the charges through this resistance.
What is meant by the “Lost Volts”?
The Potential Difference “lost” inside the cell due to Internal Resistance.
What is meant by the “Terminal potential difference” of a cell?
The voltage availbale to the external circuit. It is displayed on a voltmeter connected to the terminals of the cell. It is equal to the value of the E.M.F. minus the Lost Volts.
How can the EMF of a cell be found from a graph of I v V?
The EMF = the Y intercept
How can the internal resistance of a cell be found from a graph of I v V?
The internal resistance = - gradient
What is meant by the short circuit current of a circuit?
The maximum current possible provided by a cell. It occurs when all voltage is lost within the cell, due to a negligble resistance connector applied across its terminals (eg a spanner).
How can the short circuit current of a cell be found from a graph of I v V?
The short circuit current = the X intercept
What is meant by the “Peak voltage” of an AC supply?
The maximum voltage of the cycle.
What is meant by the “RMS voltage” of an AC supply?
The average voltage of the supply. It is the equivalent voltage to a DC supply.
What is meant by the “Peak current” of an AC supply?
The maximum current of the cycle.
What is meant by the “RMS current “ of an AC supply?
The average current of the supply.
How is the “Peak voltage” of an AC signal determined using an oscilloscope?
Y gain setting and the vertical height of the trace.
How is the “frequency” of an AC signal determined using an oscilloscope?
The timebase setting and the horizontal distance between the peaks of the trace.
What is the relationship between the “Capacitance” of a capacitor and the “Charge time”?
The greater the capacitance, the greater the charge time.
What is the relationship between the “Resistance” of a capacitor circuit and the “Charge time”?
The greater the resistance, the greater the charge time.
How can the “Energy stored” by a capacitor be determined from a V v Q graph?
The energy stored is equal to the area under the graph.
For a conductor, describe the condition of the the outermost electron shell.
Unfilled outermost shell, allowing conduction.
For an insulator, describe the condition of the the outermost electron shell.
Full outermost shell, does not allow conduction.
What is meant by the “Valence band” of an atom?
Outermost band that contains electrons. Electrons within the valence band are bound to the atom.
What is meant by the “Conduction band” of an atom?
Electrons with energies in the conduction band are free to move through the material, giving an electric current.
What is meant by the “Band gap” of an atom?
The gap between the Conduction band and Valence band of an atom.
Describe the “Band gap” of a conductor.
No Band gap. Conduction and Valence bands overlap.
Describe the “Band gap” of an insulator.
Large Band gap. Conduction only occurs at very high voltages.
Describe the “Band gap” of a semi-conductor.
Small Band gap. Some conduction can occur at room temperature.
What is meant by “Doping” a semi-conductor?
The addition of impurities to a pure semi-conductor to increase its conductivity.
In a “N-type semi-conductor”, descirbe the charge carriers.
Negative charge carriers - Electrons
In a “N-type semi-conductor”, descirbe the charge carriers.
Positive charge carriers - Holes
What is the overall electrical charge of a “N-type semi-conductor”?
Neutral / No charge
What is the overall electrical charge of a “P-type semi-conductor”?
Neutral / No charge
What is meant by the “Depletion layer” within a P-N junction?
The area of contact between the two types of semi-conductor. A small voltage is grenerated across it due to a lack of free charge carriers here.
Describe the orientation of the P-N juction in an L.E.D. that is “Forward biased”.
The P-type is connected to the positive terminal, and the N-type is connected tot he negative terminal.
Describe the orientation of the P-N juction in an L.E.D. that is “Reverse biased”.
The P-type is connected to the negative terminal, and the N-type is connected tot he positive terminal.
What is meant by the “Switch on voltage” of a diode?
The minimum applied voltage to overcome the depletion layer of a forward biased diode.
What is meant by the “Photovoltaic effect”?
The generation of a voltage within a solar cell when photons of light are incident upon it.
