<span>C. As a metal comb is held near an object with a negative charge, the comb becomes charged.
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Answer:
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:

Answer:
The system's Mean Time to Failure is 1,041.
hours
Explanation:
The number of independent identical motors = 4
The failure rate of each motor, λ = 0.002 failures per hour
Given that in order for the system to work, at least one of the motors must operate, therefore, the system are in parallel
The Mean Time to Failure for a parallel system of four identical components is given as follows;

Which gives;

The system's Mean Time to Failure = 1,041.
hours.