Best Tutorial on Ohm’s Law

In this tutorial, we are going to learn about Ohm’s Law.

Ohm’s Law – It is a set equations which show various electrical relate to each other. This law is based on a very simple principle.

  • Circuit dynamic are viewed in 1 second increment of time.
  • There are direct and indirect effects between circuit elements.

 The Basic Principle of Ohm’s Law:

  • That 1 volt of electrical pressure (Voltage) can push 1(Ampere) of current flow through 1(Ohm) of resistance. Over 1 second of time this will consume 1-watt of energy in heat or light and deplete 1 joule of stored energy. Ohm’s Law is equated to the mathematical formulas of -V or E = Voltage, I = Current, P = Power, and R = Resistance.
  • P (Power) = Current (I) * Voltage (V), with this formula Ohm’s law which current and voltage have a direct relationship. With an increase in voltage or current, Power will increase. When voltage doubles, power double, as current doubles, power doubles. If an increase in current is caused by an increased voltage then both will have an effect on increases in power use and the relationship will compound by how each factor increased.
  • Another formula for power consumption is Power (P) = I*I*R the square of current times resistance. In this formula, the current change has a multiple affect on power consumption. For example, you are pushing 10 amps of current down a 100 foot wire with a resistance of 3 Ohms. The power consumption in the wire would be 300 watts; if you push 20 amps down the same wire then power consumption would be 1200 watts. This is four times increase of power based on doubling the current.  An increase of one element such as voltage can result in increases in current flow in the circuit.
  • The formula for power is:

P = I2 * R – current has a squaring affect with resistance

P = I * V – current has a direct affect with voltage or current.

Ohms law can be used to analyze and design circuit.  An easy method to use is the Ohms law circles as shown below image. Cover up what you want and do the calculations of the other two factors.

Using these wheels, V = I* R, I = V/R, R =V/I

P = I * V, I = P/V, V = P/I in additional, remember that P = I2* R

Covering up one unknown will show you the formula to calculate for its value. Using Ohm’s law you must know two circuit measurements to find all other unknowns.

The technical’s view of Ohm’s Law –

Ohm’s law is generally used for circuit design. The technical may use Ohm’s law to reverse engineer (design) a circuit to aid in troubleshooting circuit faults. Having knowledge of direct or indirect affects based on circuit measurement  with Ohm’s law can be helpful  when compared to  known values  located on schematic diagrams This  can be  assist  in  circuits faults . Understand that  the ground ,neutral ,or returning  conductor  are  generally at 0V,ove  in some  circuits it  could  above ground  but for this section we  will  assume  it  finding  circuit   faults. Understand  that the ground but for this section we will assume it  is at 0 Volts .the  supply or source is at the  highest  voltage measurements ,equal to  the source  voltage . from  this  standpoint  ,every circle of circuit energy goes from source  to load and back to the source.

Measurements are  taken with electronic meters at various circuits locations  ,between the circuits connection and  ground across  a circuit device .each locations  as  measured to ground  is called  a Circuits Node . If a voltage  measurement is lower than expected it  indicates the  that the  node in the  circuit has  moved electrically towards  ground  . If the voltage measurement were higher than   expected, it would indicate that the node has moved electrically towards the source.

Let’s   look at a   circuit node with devices connected between a node and ground

In this  circuit ,the expected measurements  was 8volts;  the  metered measurement was 6volts.Based on Ohm ‘s law this would  indicate that the  resistance of load 1 increased ,  or  the resistance of  load 2  decreased .. V= I*R , in this circuit  there is only one  path  for current so the current  so the  current  must be the same for both loads  .The direct variable for  both devices is the load resistances .

Below is the example Ohm’s Law:

A 680 – Ohm resistor has a voltage drop of 30V, How much current and power is consumed in this device?

Step 1 – finding current – current is equal to I = Voltage = (V)/ Resistance (R)

I = 30V/680Ohm = 0.0441 Amps = 44.1mA

P = 44.1mA * 30V = 1.3W


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