Ele Scin Flashcards
Total power
P = v I
Power = volts x amps (Dc only)
Power in series
No Dc
2
P = I X R
Power = volts squared x rsistence
Ohm’s law
Voltage equals = resistance x current
What does I stand for?
Amperage/current
What does P stand for in an equation?
Watts /power
What does V stand for an equation?
Volts/ voltage
What does R stand for in an equation?
Resistance/ oems
Which way does electricity flow in a diagram?
From positive to negative
What are the three possible effects of an electric current?
Thermal
Chemical
Magnetic
Kirchoffs current law
The sum of current arriving at a point must be equal to the sum of current leaving that point
(parallel circuit only)
Kirchoff’s voltage law
The sum of the voltage around a current is equal to 0 or (the supply voltage)
In other words the total voltage drop has to equal the supply voltage
Power equation with resistance in parallel
Power = voltage squared over resistance
2
P = v / R
What is the resistivty of copper
-9
17.2 x 10 Ohm meter
What is the resistivity of Aluminium
-9
26.5 x 10 ohm meter
How to calculate flux denstity
2
Fux (Weber) divided by area (cm ) = fux density in Tesla (t)
Resistance in cross-sectional area is
Inversely proportional to its area
How to calculate Resistance
With resistivity
Length and cross-sectional area
Resistance= resistance( ohms) x length(m) divided by cross-sectional area/ csa in (m squared )
How to calculate magnetic flux density
Magnetic flux ( in Tesla T / webers per square meter / wb/m squared) divided by cross-sectional area of flux ( m square)
B=\o/A
How to calculate EMF
Electromagnetic force
e=B x l x v
/
EMS in (v) = magnetic flux in (t) x length of conductor in (m) x velocity of conductor(m/s)
Induced EMF in volts
Magnetic flux in Tesla
Length of conductor in metre
Velocity of conductors in metre per second
In what direction does magnetism flow?
North to south
What is the force that “pushes” electrons arectrocal circuit
E m f
Electron motive force
What are the components of an electromagnet?
A solenoid ( coiled wire) and a metal core
Normally steal
Which electrical component is used in modern dimmer switches?
Triac
A preset temperature of an immersion heater is maintained by
A thermostat
The voltage of an alternator is shown in
Sinusidal wavefrom
What is the definition of one ampere
1 ampere = 1 coulomb per
Second
What type of meter uses a small voltage and current to determine its value?
Ohmmeter
What is the SI unit for capacitance
Farad
What is the formula for energy?
P = w/t
Power equals watts divided by time?
How do you determine voltage in a circuit?
Watts / amperes
What are the three types of resistors?
Fixed resistor , variable resistor
Light dependent resistor
What is the equation for effort?
In leathers
Load times load to Velcro distance
Divided by effort to Fulcrum distance
The meter used in an electrical installation for recording the energy used is called
a kilowatt hour meter
The steady flow of a large amount of electrons is
Current
The frequency of an alternating current 1/1 (AC) is the…
Number of cycles per second
What is the SI unit for mass?
As well as it’s quantitive symbol
Kg and m
The St unit of weight is the…
Newtons
An electromagnetic device which allows 1/1 a high current circuit to be controlled by a low current switch is known as
A Relay
What must you times Celsius by to get to Kelvin?
-273.15
