If the 0.09-mm-diameter tungsten filament in a light bulb is to have a resistance of 0.11 Ω at 20∘C, how long should it be?

Length L=0.0125 m

Explanation:

Given data

Resistance R=0.11Ω

Temperature T=20°C

Resistivity of tungsten at 20°C p=5.6×10⁻⁸Ω.m²

Radius of filament r=0.09/2 =0.045 mm =0.045×10⁻³m

To find

Length of filament L

Solution

The Cross section of area of filament is given as:

The Resistance of a material is given as:

the answer is d. 4

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a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation: