I have a circuit with a bulb of 12 v and 21 watts I want to replace the bulb with Resistance so how much ohms?

Question

Nice Answers
but can any one guide me what else I can use instead of bulb of (12v/21watts)
because i don't need light but i want to add same load in circuit ?thanks

Answer 1

12v^2 / 21 = 6.86 ohms
volts ^2 / watts = ohms

Remember resistance changes with heat. So measuring the current and voltages will give you the proper resistance you will need. I suggest you us a variable resistor this way you can tweak it for what you need.
The12volt.com is a good calculators

Answer 2

Bulb ratings: 12 volts and 21 watts.

I will assume this a DC application

Watts = Voltage x Current
Resistance = Voltage ÷ Current

21 W = 12 V x Current.
Solving for current: Current = 21 W ÷ 12 V = 1.75 amps

The resistance of the bulb is 12 V ÷ 1.75 A = 6.86 Ω

Answer 3

The power of the bulb is 21 watts and the voltage 12
The formula For the power is V x I = P
V is the voltage, I the amperes and P the power, so we have
I = P / V I = 21 / 12 = 1.75 Amperes. Apply the ohms law we have V = R x I ( R is the resistance in ohms ) so
R = V / I R = 12 / 1.75 = 6.8571 ohms so you must replace the bulb for a resistance of 6.8571 ohms

Answer 4

Transposing, R = V^2/P

= 144/21 =~7 ohms, realizing that of course, your resistor (or equivalent resistors) need to total at least 21 W.

Resistance is futile, when it comes to a tungsten filament. It's resistance is much higher at 3000 degrees than when unlit.

Answer 5

the bulb is a current running through tungston correct? What is the resistance of tungstun? Or you could just measure it if you have the equipment.

Answer 6

ohm law states to find resistence, multiply voltage by current (amps) and the result will be resistence in ohms.

Answer 7

maybe you can find it like this:
P=(V^2)/R
21=(144)/R==>R=144/21