Resistance/ Conductance/ Ohm's Law
Milliamperes can be converted to amperes by
moving the decimal point three places to the left So 500 mA would be the same as 0.5 A
Millivolts
1/1,000 of a volt
The relationship that exists between resistance and conductance is
A reciprocal one
Small voltages
Be expressed as millivolts (mV)
The strength or intensity of the current is
Directly proportional to the voltage and inversely proportional to the resistance.
The unit of conductance is the
Simeon ( formerly the mho which is ohm spelled backwards)
Voltage can be given in a number of different units
Small voltages & Large voltages
Resistance varies inversely with the Size if the conductor in cross section in other words ?
The larger the wire , the smaller the resistance per foot of length (increases and decreases)
Ohm's Law
The relationship between voltage, current, and resistance
If the resistance of a material is known , dividing its value into 1 will
give its conductance
A reciprocal of a number
is one divided by that number
Conductance
is the ability of a material to pass electrons.
One ohm is -
is the amount of resistance that will allow one ampere of current to flow if one volt of electrical pressured is placed on a conductor.
Resistance is often expressed as
kiloohms (KΩ) or megaohms (MΩ)
Large voltages can be expressed as
kilovolts ( KV) or even megAvolts ( mV)
Resistance varies directly with the
length of wire
The formula E = I x R is used to find ?
To find the emf( voltage) when the current and the resistance is known
Thermistors decrease in resistance with an increase in
With an increase in Temperature
Thermistors
change resistance with temperature.
The factors that affect the magnitude of resistance are exactly the same for
conductance, but they affect conductance In the opposite matter
Ohms law states that voltage in volts is ?
equal to the current in amperes multiplied by the resistance in ohms This is represented by the formula E= I x R
The symbol use the represent conductance is
(S)
A KΩ (kiloohms) is
1,000 ohms
A KV is
1,000 volts
A MΩ (megaohms) is
1,000,000 ohms
mV is
1,000,000 volts
Resistance in a conductor depends on four factors
1. Material 2. Length 3. Crossectional area 4. Temperature
Milliamperes
3 places to the left
Kiloohms KΩ
3 places to the right
Converting to volts requires the decimal point to be move
6 place to the right 6 mV is than becomes 6,000,000 V
Megaohms can be converted to ohms by moving the decimal point
6 places To the right. 10MΩ would be the same as 10,000,000 Ω
Megaohms MΩ
6 places to the right
All conductors have ?
A certain amount of resistance , with some having more than others
Ohms law is very useful in
Electrical and electronics work, you will need it often to determine the missing value
The formula for conductance is
G= A/pL G= conductance measured in Siemens (s) A= cross-sectional area in cir mils L= length measured in feet P= specific resistance
Georg Ohm
German physicist who found in 1827 that in any circuit where the only opposition to the flow of electrons is resistance , there is a relationship between the values of voltage , current, resistance.
Resistance makes it possible to generate ?
Heat , control electron flow, and supply the correct voltage to a device.
To find the current when the voltage and resistance are known use
I = E/R
Resistance can be measured using an ?
Ohmmeter
When using ohms law the quantities must be expressed in ?
Ohms , amperes ,and volts If any of these quantities are given on other units these should be converted before making calculations with them
In terms of resistance and conductance
R= 1/G (conductance measured in Siemens (S) G=1/R
To find the resistance when the voltage and current is known
R=E/I
For most materials , the higher the temperature ,
The higher the resistance
Thermistors are used in certain types of meters to measure ?
Temperature
Milliamperes (mA)-
is 1/1,000 of an ampere
Current is often expressed in
milliamperes
Resistance is measure in ?
ohms
Resistance -
opposition to the flow of current
I
represents current. Current is the rate of flow of electrons , or intensity of the flow. I is the rate of charge of flow
R
represents resistance
E
represents voltage. this is best remembered as electromotive force (emf) which is another word for voltage.
Conductance is the opposite of
resistance
If the conductance is known, dividing its value into 1 will give its
resistance.
Conductance is directly proportional to area and inversely proportional to
the length and specific resistance of the material
The longer the wire or conductor
the more resistance it's has
Some materials offer more resistance than others , depending On ?
the number of free electrons present I'm the material
Converting mV to V requires that the decimal point be moved
three places to the left 1,000 mV would be the same as 1V
converting KV to V requires the decimal place to be moved
three places to the right 3KV is the same as 3,000 V
To convert kiloohms into ohms , move the decimal point
three places to the right. 6 KΩ would them become 6,000 Ω
The symbol for ohm is
Ω (omega)