# Question: please answer all questions if you have the correct answer...

###### Question details

Please answer all questions if you have the correct answer

a) A 7.0 m -long round tungsten wire is to reach a temperature
of 3300 K when a current of 12.0 A flows through it. What diameter
should the wire be? Assume the wire loses energy only by radiation
(use the the Stefan-Boltzmann equation
ΔQ/Δt=ϵσA(T^{4}_{1}−T^{4}_{2}),
where A is the area of the emitting object, T_{1} is the
temperature of the emitting object, T_{2} is the
temperature of an environment, σ is the Stefan-Boltzmann constant,
and the emissivity ϵ=1.0) and the surrounding temperature is 30
^{∘}C. Express your answer using two significant figures.
(tungsten resistivity at 3300K is 103.3)

d = ___________________mm

b) A 2.85 μF capacitor is charged to 485 V and a 3.50 μFcapacitor is charged to 500 V .

What is the charge on each capacitor if plates of opposite sign are connected? Express your answers using two significant figures