What is the relation between voltage and current

 

        Hi friends Today, I will explain, relation between voltage and current
If voltage increases then current will increase or decrease or will remain same, Many persons ask me,  you tell current will increase, you tell that current will decrease, so I will tell today, where will current increase and where will current decrease,

ohms law    

  Here, A load R is connected across AC supply, Value of R is 1 Ohm, V is the voltage across R, current flowing is I, so V/I = R, this is Ohm's law.

Voltage and current relation , relation between voltage and current

 

       Now suppose voltage is 10 Volts, then 10 amps current will flow and 10/10 = 1 Ohm will come, Now If we increase the voltage, 10 become 20, then current will also increase, but V/I, 20 voltS/ 20 ampS = 1 ohm. if, we reduce this voltage to half, then current also will becomes half and this ratio still will be 1, as value of resistance is 1 Ohm. so , when this resistance or load is fixed, then if voltage increases, then current also will increase. and current will decrease at less voltage, and Ohm's law is always followed/

 voltage and current relation in transformer

      Now suppose, a transformer is connected, between supply & amp  load, now in case of calculation with transformer, we use formula of power, power P= V* I,

      Now suppose, 10 volts  and 10 Amps current I is flowing, as it was 10 amps earlier, so how much power?, 10 * 10= 100 watts, resistance is still 1 ohm as earlier, so 10 volt voltage and 10 amp current, multiplication will be 100, this calculation is valid here,

     Now suppose, voltage at One side is more, voltage at One side becomes 50 volts from 10 volts, now what will happen? as power is same, here also 100 watts, here also 100 watts, it can be that, power here is 100 watts, but here power is 150 or 50 W, power remain same, voltage becomes 50 from 10, current will have to be less, so current will be less here, voltage become 50 from 10, current become 2 from 10 amps, now 50 Volts * 2 amps = 100 watts.

    Now if voltage increases further, voltage is 100 V now, then current will reduce further and multiplication of voltage & current, will give power as per formula, see, this formula is followed even now, this formula is derived from ohms law, but there is difference between Voltage & amp;  if we increase the voltage, current also will increase, here, if voltage increases, then current  decreases, the reason for this is, if V & amp; I calculation is done for transformer, between secondary and primary, in such calculation, power remain same, if power remain same, then for higher voltage in primary, current in primary will be less, secondary voltage & current, will not change, if we increase turn ratio, (more primary turns), turns are increased here further, by keeping turns constant here, current will reduce here further, ( as voltage is more), as voltage is increasing here, current here will go on reducing,

      so, wherever resistance is fixed, and we calculate with resistive load, then current increases with voltage increase, and formula used is R = V/I, but in the case of transformer , then we consider power,primary side power and secondary side power is equal, that time, multiplication of P & amp; I remains constant. so with increase in voltage, current will start decreasing, so  both the formulas are working, here,

Voltage and current relationship in ac circuits, voltage and current relationship

 

    Now in  a UPS , input of UPS is AC and UPS is charging a battery, Good quality UPS, keep the charging current constant, if current is required to be changed, then also current will be fixed ( with time), only setting will change like 10 A or 5 A, if voltage is changing or with change in battery voltage, this charging current will not change, so, in this case, if voltage is increasing, current will neither increase, current will not reduce with less in voltage, current remains fixed,

        But Ohm's law is still followed here, V/R = I, now if voltage increases, current is same, then how can it possible?

        only way is, that R is increased, so function of UPS (in this case) is, drop in side the UPS here, or equivalent resistance inside (in series), will change with voltage, such that, current remains constant here,

       Now In a simple charger, AC supply,  rectifier,  a resistor in series and battery is charging, Ohm's law is followed here also, the current here is controlled / limited by the resistor, but what happens?, If resistance is fixed here, then current increases with increase in voltage, but Ohm's law is always followed,

ohms law use in ac circuit

         I told you 3 points so far, 1st point, in this case, with increase or decrease in voltage, current will neither increases, nor decreases, current remains same (constant), 2nd point told, was, if resistance is fixed, and we are calculating for resistance, then with increase in voltage, current will increase, and with decrease in voltage, current will decrease, 3rd point was, if we calculate for transformer, then, primary & secondary of the transformer, will have same power, that time, V X I is power, and with increase in voltage, current decreases, this happens in primary, as voltage increases here, current will go on reducing, but power remains same,

       Now, i will tell you, some more points about power, there is a equipment, there is input supply and a load is connected at output, V/R = I this is Ohm's law, this is always followed, power flowing here is P, power flowing here is load power, I have written it as P load, and one more type of power is there, that is called P loss, P loss is the power loss inside it, power flowing here, plus, this power, P load + P losses=P,

relation between voltage and current
 

       This may be possible, that load is fixed, but power P is changing, the P load is fixed, the P is changing, that is possible, if, P losses are changing, if voltage is changing, then equipment losses may change, that time, power formula will be, P = Power loss + Power load,

      Now suppose, the equipment, is a mobile charger, input of the mobile charger. Mobile is connected at the output, you must have seen in charger, that output power written is very less, but input power written is very high, input power and output power  will not be equal, the input power is more, why? due to power loss, there is power loss inside the charger, that also comes from input power.

ohms law use, ohm law explained, working of ohms law, voltage and current relationship

       I will tell few examples, like, battery charger, UPS, fan, motor, induction heater, vacuum cleaner, washing machine, bulb, whatever is here, this ohm's law is always followed, if you feel, that Ohm's law is not followed, this does not mean, that Ohm's law is wrong, Ohm's law is always correct, but our knowledge is less, we need to learn more, then you should learn more, this formula is always correct, many places,

      what happens, like in motor, induction heater, in vacuum cleaner, or in washing machine, there is no R connected, Have you seen R there? NO, that means load due to air, or load due to water, or some other type of load, but bulb has R type load, so all these loads, have some equivalent resistance, power P load flow according to that, plus, there will be losses also, then we get total power, OK ?

       Now in case of the bulb, many has asked, that Ohms law is not followed here, Formula is always followed, when bulb is cold, then value of R is very less, Current (I) will increase due to less R, but, when bulb becomes ON, then filament will be very hot, then value of R increases, so current will reduce, It happens because, value of R is changing, but you feel, that formula is not followed, formula is always followed.

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