ATAR Notes: Forum
VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: Samueliscool223 on February 14, 2020, 10:17:01 pm
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A projector lamp is designed to take a current of 4.0A when used with a 32V home lighting unit, what resistance ought to be placed in series with the lamp if it is to be used on a 240V supply?
The answer is 52 ohms, how do you get it? I thought you'd have to derive the resistance by using i=v/r ... 4=240/r
r=60, but i guess not. Please help
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A projector lamp is designed to take a current of 4.0A when used with a 32V home lighting unit, what resistance ought to be placed in series with the lamp if it is to be used on a 240V supply?
The answer is 52 ohms, how do you get it? I thought you'd have to derive the resistance by using i=v/r ... 4=240/r
r=60, but i guess not. Please help
Hey!
The whole circuit will use 240V. The lighting uses 32V. This leaves 208V for the resistor.
Assuming this circuit is in series, the current for both the light and the resistor must be the same.
\(\therefore R=\frac{V}{I}\) = \(R = \frac{208V}{4.0 A}\)
\(\therefore R = 52 \Omega\)
Hope this helps! :)
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Hey!
The whole circuit will use 240V. The lighting uses 32V. This leaves 208V for the resistor.
Assuming this circuit is in series, the current for both the light and the resistor must be the same.
\(\therefore R=\frac{V}{I}\) = \(R = \frac{208V}{4.0 A}\)
\(\therefore R = 52 \Omega\)
Hope this helps! :)
Ok I get it now, I think I mustve read the question wrong, haha. Thanks