Ohms Law Definition

Ohm’s law defines a linear relationship between the voltage and the current in an electrical circuit. The DC current flow through a resistor is set by the resistor’s voltage drop and the resistor’s resistance. With water flow analogy we can imagine the electric current as water current through pipe, the resistor as a thin pipe that limits the water flow, the voltage as height difference of the water that enables the water flow.
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Ohm’s law
Ohm’s law definition :- The resistor’s current I in amps (A) is equal to the resistor’s voltage VR=V in volts (V) divided by the resistance R in ohms (Ω)
V is the voltage drop of the resistor, measured in Volts (V). Sometimes E is used instead of V . E denotes electromotive force. I is the electrical current fl0wing through the resistor, measured in Amperes (A) R is the resistance of the resistor, measured in Ohms (Ω)
Voltage calculation
When we know the current and resistance, we can calculate the voltage. The voltage V in volts (V) is equal to the to the current I in amps (A) times the resistance R in ohms (Ω):
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Resistance calculation
When we know the voltage and the current, we can calculate the resistance. The resistance R in ohms (Ω) is equal to the voltage V in volts (V) divided by the current I in amps (A)
Since the current is set by the values of the voltage and resistance, the Ohm’s law formula can show that:

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If we increase the voltage, the current will increase.
If we increase the resistance, the current will reduce.
Example =1 Find the current of an electrical circuit that has resistance of 50 Ohms and power supply of 5 Volts.

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Solution:V = 5V
R = 220Ω
I = V / R = 5V / 220Ω = 0.02A = 22 mA.
Unit Name Unit Symbol Quantity.

Unit Name

Unit Symbol

Quantity

Ampere (amp) A Electric current (I)
Volt V Voltage (V, E)Electromotive force (E)Electric potential (φ)
Ohm Ω Resistance (R)Impedance (Z)
Watt W Electric power (P)
Decibel-milliwatt dBm Electric power (P)
Decibel-Watt dBW Electric power (P)
Volt-Ampere-Reactive VAR Reactive power (Q)
Volt-Ampere VA Apparent power (S)
Farad F Capacitance (C)
Henry H Inductance (L)
siemens / mho S Conductance (G)Admittance (Y)
Coulomb C Electric charge (Q)
Ampere-hour A·h Electric charge (Q)
Joule J Energy (E)
Kilowatt-hour kWh Energy (E)
Electron-volt eV Energy (E)
Ohm-meter Ω∙m Resistivity (ρ)
siemens per meter S/m Conductivity (σ)
Volts per meter V/m Electric field (E)
Newtons per coulomb N/C Electric field (E)
Volt-meter V·m Electric flux (Φe)
Tesla T Magnetic field (B)
Gauss G Magnetic field (B)
Weber Wb Magnetic flux (Φm)
Hertz Hz Frequency (f)
Seconds s Time (t)
Meter / metre m Length (l)
Square-meter m2 Area (A)
Decibel dB

Parts per million

ppm

Units prefix table

Prefix 

PrefixSymbol 

Prefix factor

Example

pico

p

10-12

1pF = 10-12F

nano

n

10-9

1nF = 10-9F

micro

μ

10-6

1μA = 10-6A

milli

m

10-3

1mA = 10-3A

kilo

K

10 3

1KΩ = 1000Ω

mega

M

10 6

1MHz = 106Hz

giga

G

10 9

1GHz = 109Hz

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