Explain Ohm's Law | Define Ohm's Law

 

Resistance

This property restricts electric current to flow, means resistance stop the current for passing, resistance or impedance measure in Ohm’s.

When the current flows in any wire it will face to some resistance, but any conductor has very low resistance means 2-3 ohms or may be some above, and insulator has very high resistance like mega ohms, this matter that Conductor can pass current easily and insulator cannot pass current. Other disadvantage of resistance that when current pass from wire, so wires getting heat by case of resistance, heat amount has depended on wire’s diameter (Cross Section Area), and resistance depended on diameter.

If you want that, why resistance depended on diameter you can known it.

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Ohm’s Law:-

 Ohm is name the man who discovered this law his full name is Georg Simon Ohm, and this law tells relationship between voltage, current and resistance. Ohms law is mostly use full and most fundamental laws for understand electrical study, this formula connect three basic units such as Voltage, Current and Resistance, and learn to us this three quantities in one relationship.

The electrical and electronics has based on three fundamental units “Voltage, Current, & Resistance” any circuit has depended on this three quantities. Any circuit complete when this three properties will fulfill, any circuit can't complete without any one quantity from this three quantities.

The Georg Simon Ohm has given a formula which easily defined this relation.

The electrical current is directly proportional to voltage and inversely proportional to the resistance, directly proportional means when voltage will increase then current also increase, but may be some conditions will be apply which we will discuss about below, and inversely proportional when resistance will increase then current be decrease.

All electrical equipment has resistance therefore appliances control the current, but each one appliances having different resistance. In electrical field resistance has big character, therefore over all appliances operate in the under control current, if resistance not exist then we cannot operate anyone equipment easily, because if conductor connect directly across a battery therefore a lot of current would flow, hence all current will wasted.

Ohm’s law Formula: - V = I x R

 

This formula mostly used on any place, our all appliances operates on it.

“V” denoted to Voltage,

“I”   denoted to Current

“R” denoted to Resistance

Voltage is the source of current, and resistance will restrict of current.

Ohm's Law Example:-

We have a 2.5v “Led”, and want to glow it by 12v battery, if this battery connect directly to “Led” then Led will burnt, because “Led” required 2.5v, so we will attach a resistance in series with the "Led" and can safely glow it, But which value’s resistance  can connect with “Led” this confusion will remove by this formula.

 

Ohm’s laws says that, we need any two values for calculate the Resistance value.

!...This formula drive by three method…1

1-     V = I x R

2-     R = V ÷ I

3-     I = V ÷ R

 

Here we want find to resistance so we need Led’s voltage and it’s current.

Ohm’s Law Example:-

Battery is 12v

LED is 2.5v

LED current is 25 mA

Drive Formula:-

Use Second Method

Step 1:-

12v – 2.5v = 9.5v

Now we will take “9.5v” because this voltage wants to drop.

Step 2:- R = V ÷ I

Arrange with mathematically

V ÷ I = R

But here we can’t take Current in mA so first convert mA to Ampere,

1 Ampere equal to 1000 mA

Solve:- 25 ÷ 1000 = 0.025

Apply Ohm’s Law

9.5 ÷ 0.025 = 380 Ohm

It means that we can use “380” ohm’s resistance for glow 2.5v 25mA “Led”.

Now discus about current that directly proportional to voltage it means, where current will be change with the voltage changing, if power or losses has constant so current will increase if voltage decrease. If on same condition, means power and losses have constant, current will be decrease if voltage increase.

Suppose

Example 1:-

We have a single phase motor its power is 500 watt and power factor is unity means “1” it need 230v AC voltage

Apply Current formula

I = P ÷ V x Power Factor

I is current

P is power

V is voltage

Note:- Power rated in Watts means P is watts which given above

Current = 500 ÷ 230

After solved

Current is 2.17

Means this motor consume 2.17 Ampere current on 230 Voltage

Note:- Let know that power is fixed of each appliances don't matter that equipment is DC or AC.

Example 2:-

Take above example but some values is change

A motor of 500 watts and Power factor is "unity" means “1” and required voltage is 150v.

Calculate Current

Same formula:-

I = P ÷ V x Power Factor

Current = 500 ÷ 150

Current is 3.33 Ampere

You seen that current has been increased because voltage decreased, and above “example one” show that current is low because voltage is high, same like this formula can work any place, you can try another place and see result.