Electronics III Flashcards
Electric current is the flow of ________ _______.
electric charge
Electric charge is carried by particles such as _________ and _____.
electrons
ions
In metals, the charge carriers are negatively charged __________ ________.
conduction electrons
Conduction electrons move about inside the ______, repeatedly _________ with each other and the fixed positive _____ of the metal.
metal
colliding
ions
Good conductors have many free to move ________ ________.
charge carriers
Insulators have few ________ ________.
charge carriers
When the ___________ of a semiconductor is _________ more charge carriers are produced and the semiconductor turns from an _________ into a _________.
temperature
increased
insulator
conductor
In electric circuits the current is considered to flow out of the ________ terminal of a power supply and into the _________ terminal.
positive
negative
A _______ gives each electron a fixed amount of _______.
battery
energy
Chemical energy is transformed into ________ potential energy.
electrical
______ has to be done to pass electrons through devices like the bulb.
Work
Metals and other good conductors have very ____ resistivities.
(e.g. copper = 1.7 x 10 – 8 Ωm)
low
Good insulators have very _____ resistivities.
e.g. PVC = 1.0 x 10 + 14 Ωm
high
Semiconductors have ___________ resistivities.
e.g. silicon = 2.3 x 10 + 3 Ωm
intermediate
Filament lamp, resistance __________ at higher currents due to increasing ___________.
increases
temperature
A filament lamp does not obey ______ law.
Ohm’s
Thermistor, resistance __________ with increasing temperature.
decreases
A thermistor obeys Ohm’s law if the ___________ remains _________.
temperature
constant
Metallic conductors, resistance _________ relatively _______ with temperature.
increases
slowly
Positive ions within a conductor _______ more with increasing temperature
vibrate
Semiconductors, resistance __________ relatively ________ with temperature.
decreases
quickly
At any junction in a circuit, the total current ________ the junction is equal to the total current _________ the junction.
leaving
entering
Resistors in series pass the same ________.
current
The total _______ across two resistors, V, is equal to the sum of the individual voltage V1 and V2.
V = V1 + V2
voltage
The total resistance is always ________ than any of the individual resistances.
greater
Resistors in parallel all have the same _______.
voltage
The total _______ through the two resistors, I, is equal to the sum of the individual currents I1 and 12.
I = I1 + I2
current
The total resistance is always ________ than any of the individual resistances.
smaller
When an electric ________ flows through an electrical conductor the ___________ of the conductor causes the conductor to be _______.
current
resistance
heated
A car battery has an emf of about _____.
12V
A high voltage power supply sometimes has a large protective ________ resistance.
internal
Internal resistance limits the _______ that can be supplied to be well below the fatal level of about _____.
current
50 mA
A potential divider consists of ____ or more resistors connected in ______ across a source of ______ potential difference.
two
series
fixed
A potential divider is used in many circuits to control the level of an _______.
output
List two examples of using a potential divider
- Volume control
2. Automatic light control
A capacitor is a device for storing _________ charge.
electrical
Most capacitors consist of two parallel __________ (plates) separated by a ________.
conductors
dielectric
A dielectric is a material which is a _____ conductor of electricity however it can be _________ by an applied _______ field.
poor
polarised
electric
Uses of capacitors include:
Voltage regulation in power supplies
Timing circuits
Tuning circuits
Back-up power supplies
When a voltage is connected to the capacitor _________ flow off one of the ________ plates and onto the ________ plates.
electrons
positive
negative
The ____________ of a capacitor is defined as the _______ stored per unit potential difference change.
capacitance
charge
Time constant is the time taken for a capacitor to discharge to _____ of its ______ charge.
0.37
initial
The potential difference across a device is equal to the _____ _____ per unit ______ passing through the device.
work done
charge
The electromotive force (emf) of a power supply is equal to the _______ supplied per unit _______ by the power supply.
energy
charge
1 volt is equivalent to?
1 joule per coloumb
