Question

Please I need some major help!! Physics emergency!

Find the length of the Tungsten filament (resistivity = 5.6e-8 Ohm-meters and diameter = .004 mm) of an individual bulb in the diagram above if the ammeter reads 0.16 amps and the bulbs are dissipating 6 Watts each.

Answer 1

Power in a circuit =\[I ^{2}R\]

You have I and P so you can calculate R

But for the wire
\[R=\frac{ rhoL }{ A }\] (where rho = resistivity)

You know rho, A and R so ypu can calculate L

Answer 2

Be careful with units - especialy in calculatin area - rho has units in Meters - you must calculate the area in sqm (not mm)

Answer 3

units were my mistake!! thanks you so much!