What registance is needed to operate 4.5 V toy form 12 V battary?

Question

What registance is needed to operate 4.5 V toy form 12 V battary?

Answer 1

hey I think its

                   V = V1 + V2

                   V = 4.5 + 12

Therefore V = 16.5 V



                  Total Resistance = V / 1

                                           = 16.5 / 1

                                           = 16.5 ohms........

I hope this helps and hope this is what u r looking for.......... [:)]

Answer 2

$10 says you damage the toy or start a fire trying it.

If you are asking this question, you clearly have no idea what you are doing.  The other responses are more or less correct assuming that your toy is a resistive load (no motors) and consumes a constant amount of current from the 4.5V power source.  Both of these assumptions are probably false.

In order to operate your toy, you will need to build a voltage regulation circuit.  This will consist of two capacitors, and a voltage regulator chip (at least).  You must take into account peak power demand and heat dissipation.  Heat is an issue because power is lost dropping the voltage from 12 to 4.5.  Clearly the design of such a thing is beyond the scope of what can reasonably be put into an answer here.  

Suffice it to say that the answer in practice is more complicated than what you learn in a high school or even first-year college physics unit on circuits, ohm's law, etc.

Answer 3

as resistance = voltage/current

if there is no current then there is no need for applying the resistance

Answer 4

This depends on the resistance of the toy.  The formula will be r/T=(r+R)/B, where r is the resistance of the toy, T is the voltage to the toy, R= the extra resistor's resistance, and B equals the voltage of the battery.  Solving for R:

R=rB/T-r

Remember than in using a resistor to absorb the extra power, you're going to be wasting almost 2/3rds of the battery's energy.  Depending on the power drain, the extra heat could be significant.

Answer 5

Your question is not clear.( 4.5V toyand 12V battary),  

Answer 6

V = I R, whats the amperage (I)?  

Answer 7

To work out the resistance required you will need to know the current draw of the toy at 4.5 volts.

Once that is known it is a case of ohms law. E/I=R.

Lets say the toy draws 1 amp.

The toy needing only 4.5 means we need 7.5 volts across our resistor. Now we have two parts of the equation E=7.5v and I= 1A.

7.5/1=7.5R. In this case it is 7.5 ohms but in reality it will be some thing else.

Here is a much easier way to do it. Buy a 5 volt regulator and wire that in.

The regulator is called a 7805. Info can be found on the net on how it is wired. It is very simple and much better if the load varies on the toy.