Electricity 15: Concepts, terms, and SI Units Flashcards
Electricity that flows in only one direction is…
DC or Direct Current
Continually alternates direction (current)
AC Alternating Current
Why do electrons move from one place to another?
Because of the attraction and repulsion between electric charges
Does the wire carrying a current have an overall charge?
NO
The force with which an electric current flows is…
voltage
What is the SI unit of voltage?
volt
What is an instrument that measures voltage ?
voltmeter
What is the amount of charge flowing past a given point in a certain amount of time? ( Rate of charge flow)
Current
What is the SI unit of current?
Ampere —or informally the amp
What is the instrument that measures current
ammeter
What is the energy used per unit time; what is the formula that goes along with it? What is the SI unit?
Power;
P= VI; Power= Voltage(Current)
Watt
The amount of electrical energy used by the electrical device can be described by what term? And what is the formula for it (basically)?
The kilowatt-hour
kW•hr = power/ amount of time used (in hours)
What are objects that conduct electricity well?
conductor
Materials that do not carry current well are
insulator
If objects neither conduct or insulate… what are they?
Semiconductors
The amount a certain object hinders electron flow is
resistance
The unit of resistance is the
ohm, symbolized by omega
The instrument to measure resistance is the
ohmmeter
the energy used to overcome resistance is
Joule heat
What are the four factors that can reduce resistance
Type of material
Length of conductor
Diameter of conductor
Temperature
What law states that the current flowing through a conductor is directly proportional to the voltage and inversely proportional to the resistance? What is the formula stated out?
Ohm’s law
V= IR Voltage=Current(Resistance)
any electrical device designed to add resistance to a circuit is the
resistor
the path of electrical current is
electrical circuit
What three parts do an electrical circuit contain? Hint: May be a battery or generator Carries electrons around the circuit Transforms energy into useful energy
Source of current
Conductors
Load
A circuit that contains a complete path for the electrons to follow is a
One that does not allow for complete flow?
closed circuit
open circuit
the flow of current through a circuit can be controlled by a
switch
a narrow strip of metal housed in a protective case that cannot be replaced after blowing out is a
fuse
an automatic switch that opens the circuit when current flowing through it exceeds a curtain amount is a
circuit breaker
Fuses and circuit breakers not only help with short circuits, but also they help a situation when there are too many appliances plugged in to one circuit
overloaded circuit
There is another method of safety with circuits to prevent electrocution
grounding
Series Circuit
What is it’s relation to resistance voltage and current?
Current — Same
Resistance — equals the resistances of all the loads added up
Voltage — divided amongst the loads
Parallel
What is the relation between current, resistance and voltage?
Current— divided among the loads
Resistance — the total resistance is decreased as more loads are added in parallel to the circuit
Voltage— the same throughout
What produces light by heating a thin wire or filament to extremely hot?
Incandescent lamp
What produces light by passing an electric current through a long tube filled with a low pressure mixture of mercury vapor and argon?
Fluorescent lamp
What produces light by using semiconductors when direct current is applied
LEDs, or light-emitting diodes
what converts electricity to back and forth motion ; Describe it
Solenoid
A wire with an iron coil with an iron bar free to slide — with a ball
an electrical switch operated by an electromagnet is a …
relay
What are the three main parts of the DC Motor?
What are the last part used for ?
Field magnet
Armature
Commutator
The commutator is used for reversing the current
What are the three main parts of the AC Motor?
What is the last one used for?
Field Magnet
Armature
Slip Rings
They are used for not getting the wires tangled up
The negative terminal contacts the cell’s…
The positive terminal contacts the cell’s …
anode
cathode
cells can be arranged in series to boost …
voltage
a group of electrochemical cells connected as a single source of current is the …
Battery
cells can be arranged in parallel to boost the…
current
The ability of magnetism to convert mechanical motion into electric current is called
electromagnetic induction
What is a device that detects and measures very small electrical currents?
galvanometer
To produce current, the lines of magnetic flux must be ….
cut
What are the ways that the strength of magnetically induced current can be increased?
Strength of magnet( the more strength the better)
Speed of the magnet ( the more speed the better)
Number of coils ( the more the better)
a devise that uses electromagnetic induction is a
The AC generator produces
generator
large amounts of electricity
What can recharge the battery of an automobile?
alternators
What generator uses a conducting fluid passing through a magnetic field at a high speed?
Magnetohydrodynamic generator
When it is necessary to increase or decrease the voltage of an electric current— you can use a
More -
Less-
SU-
SD-
transformer
Step-up
step-down
I= Less voltage more current; O= more voltage less current after
I= more voltage less current; O= less current more voltage
