Each battery has an emf of 1.5 volts. The length of the tungsten filament in eac

Question

Each battery has an emf of1.5volts. The length of the tungsten filament in each bulb is0.015m. The radius of the filament is 5e-6 m (it is very thin!). The electron mobility of tungsten is 1.8e-3 (m/s)/(V/m). Tungsten has 6e+28 mobile electrons per cubic meter.

Since there are three unknown quantities, we need three equations relating these quantities. Use any two valid energy conservation equations and one valid charge conservation equation to solve for the following electric field magnitudes:

What is the magnitude of the electric field inside bulb #1?

What is the magnitude of the electric field inside bulb #2?

How many electrons per second enter bulb #1?

How many electrons per second enter bulb #2?

Explanation / Answer

Last part of #4:
E1=(4*emf)/3L
E2=(2*emf)/3L
i1=nAu(E1)
i2= .5*(i1) --> or you could do n*A*u*E2 again

where n=6e28 e- / m^3
u=1.8e-3 (m/s)/(V/m)
and A=pi*(5e-6)^2 m^2

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