I want to limit a 3A current to 1A.
2007-06-17 14:35:48 · 7 answers · asked by Ma77hew 3 in Science & Mathematics ➔ Physics
srry 9v is what i have
2007-06-17 14:52:03 · update #1
All these answers are fine if you simply want to drain some current from your 9v source to ground. But it's never that simple in real life. You're probably driving some load that wants 1A at some voltage less than 9v, call it Vload. Then you want a resistor that produces the desired voltage drop at the desired current, i.e., such that (9v - Vload) / R = 1A which reduces to R = (9 - Vload) ohms.
2007-06-17 16:18:40 · answer #1 · answered by kirchwey 7 · 0⤊ 0⤋
To determine the resistance value plug the voltage and current into this formula: E=I*R where E is the voltage in volts,I is the current in amps and R is the resistance in ohms. Rearranging the formula you get R=E/I. If the voltage is 9 volts and the current you desire is 1 amp the resistor will be 9 ohms.
Another part of the project you will be concerned with is the physical size of the resistor, which determines how much Wattage the resistor can carry without burning up.
P = I^2 • R, where P = Power in watts, I = current in amps, R=resistance in ohms.
P=1^2*9
P=1*9
P=9 watts
You can probably find a 9 ohm 10 watt resistor at your local electronics supply store. This is the total resistance needed on a 9 volt circuit to limit the current to 1 amp. If the resistance in the circuit cannot be removed then subtract the value currently in place from the 9 ohms and place that much resistance in the circuit. Being aware as before of the wattage limitations of the resistance currently in the circuit.
Good luck with this.
2007-06-17 21:52:45 · answer #2 · answered by Gerald D 2 · 0⤊ 0⤋
Depends on the voltage .Using R=V/I, We have V/R=3A. So to have 1A, and assume we have 3V, you need a 3 ohm resistor. If you have 6 V, you should use a 6 ohm resistor to get 1A.
2007-06-17 21:44:20 · answer #3 · answered by yongchunhon 2 · 0⤊ 0⤋
Keeping V the same,
V = I2 R2 = I1 R1
R2/ R1 = I1 / I2
R2/R1 = (3/1) = 3
R2 = 3 R1.
Add two more resistances R1 in series
2007-06-17 22:54:08 · answer #4 · answered by Pearlsawme 7 · 0⤊ 0⤋
V=IR
so if you want to decrease current by 1/3..
you need to increase resistance by 1/3 or..
decrease your voltage by 1/3.
2007-06-17 21:44:26 · answer #5 · answered by kennyk 4 · 0⤊ 0⤋
Your question is not providing any data about voltage.
Current and resistance are inversely related. Therefore if you increase the resistance (which can happen if you connect them in series) then the current will reduce.
2007-06-17 21:41:53 · answer #6 · answered by ping_anand 3 · 0⤊ 0⤋
9 ohms.
2007-06-20 12:03:39 · answer #7 · answered by johnandeileen2000 7 · 0⤊ 0⤋