what kind of resistor would you need to convert 9 volts to 7 volts?

Question

for a rc car....what ohm

Answer 1

You can't with a single resistor. Like the first guy said, you would need to make a voltage divider circuit consisting of at least two resistors.

Try this:

Answer 2

far extra suggestion is mandatory with the intention to effectively propose you on your undertaking. could understand what the device is and the type you intend to apply it; what its optimal and minimum modern draw is from the 7.5 volt AA battery source. in case you will locate out what the optimal modern is that the device attracts from the 5 AA batteries, use here to calculate the sequence resistor fee: Rs = ( 9v - 7.5v / I max.) = a million.5 volts / I max. modern. as an occasion: if your device attracts 0.a million A or (one hundred mA) from the batteries decrease than optimal load, the resistor to apply in sequence with the 9 volt battery would be: a million.5 v /0.a million A = 15 ohms. the size (wattage) of the resistor would be: P = I^2 x R or resistor length (0.a million A) x (0.a million A) x 15 ohms = 0.a hundred and fifty Watts. to supply your self a margin of protection, you will pick a fifteen ohm resistor with a minimum of two times the calculated length, or 0.3 hundred Watts. in this occasion, the resistor you will purchase is 15 ohms at a million/2 Watt length. a million/2 Watt is comparable to 0.500 Watts which continues to be small yet sufficiently great that it will no longer incredibly deplete in case of a quick circuit or something. Now that replaced right into a calculation for an occasion resistor. The resistor you fairly choose on your circuit relies upon on the optimal modern the device attracts from the 5 AA batteries, whilst the device is working huge open (each and every little thing on and working). See in case you may get that suggestion from the specification sheet that got here with the device, or from an internet seek. terrific regards

Answer 3

You would need to use a potential divider. They consist of 2 resistors in series so you can tap off voltage from in between.

To be able to get 7 volts you could use resistors of 2KOhm and 7KOhm. Or any resistors with the same ratio.

You would have to use values that are about 10 times less than the resistance of the rest of the circuit (I am not sure what this would be, you could use V=I/R to work this out) to make sure to much current isn't drained which would stop the potential didvder working correctly

Answer 4

How much current does the RC car draw?

You can find a zener diode to drop about 2volts, but you need a resistor (in parallel) to handle the current. Use R = E/I to set resistor value.

A cct needing 200mA would need a 10 ohm resistor.

Answer 5

all depends on the current.
R = V/I

R is resistance in ohms
V = DC volts
I = current.

however- I'll bet the car isn't a linear system- so the value of I will actually change with the available voltage.

er... never mind. Andy's solution is better. For some reason I was limiting my answer to a single resistor.