Basic of eee Ohm's law

Ohm's Law

Ohm's law shows a linear relationship between the voltage and the current in an electrical circuit.

Ohm's law formula

The resistor's current I in amps (A) is equal to the resistor's voltage V in volts (V) divided by the resistance R in ohms (Ω):

V is the voltage drop of the resistor, measured in Volts (V). In some cases Ohm's law uses the letter E to represent voltage. Edenotes electromotive force.

I is the electrical current flowing 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):

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:

• 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 voltage supply of 5 Volts.

Solution:

V = 5V

R = 50Ω

I = V / R = 5V / 50Ω = 0.1A = 100mA

Example #2

Find the resistance of an electrical circuit that has voltage supply of 10 Volts and current of 5mA.

Solution:

V = 10V

I = 5mA = 0.005A

R = V / I = 10V / 0.005A = 2000Ω = 2kΩ

Ohm's Law for AC Circuit

The load's current I in amps (A) is equal to the load's voltage V_Z=V in volts (V) divided by the impedance Z in ohms (Ω):

V is the voltage drop on the load, measured in Volts (V)

I is the electrical current, measured in Amps (A)

Z is the impedance of the load, measured in Ohms (Ω)

Example #3

Find the current of an AC circuit, that has voltage supply of 110V∟70° and load of 0.5kΩ∟20°.

Solution:

V = 110V∟70°

Z = 0.5kΩ∟20° = 500Ω∟20°

I = V / Z = 110V∟70° / 500Ω∟20° = (110V / 500Ω) ∟ (70°-20°) = 0.22A ∟50°