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:
Explanation:
Below is an attachment containing the solution.
Complete question:
A fireman of mass 80 kg slides down a pole. When he reaches the bottom, 4.2 m below his starting point, his speed is 2.2 m/s. By how much has thermal energy increased during his slide?
Answer:
The thermal energy increased by 3,099.2 J
Explanation:
Given;
mass of the fireman, m = 80 kg
initial position of the fireman, hi = 4.2 m
final speed, v = 2.2 m/s
The change in the thermal energy is calculated as;
ΔE + (K.Ef - K.Ei) + (Uf - Ui) = 0
where;
ΔE is the change in the thermal energy
K.Ef is the final kinetic energy
K.Ei is the initial kinetic energy
Uf is the final potential energy
Ui is the initial potential energy