R = ρl/A
Where R = Resistance in Ohms, Ω, ρ = Resistivity in Ωm, l = Length in m.
Area in m²
ρ = Resistivity = 3.14 * 10⁻⁸ Ωm, Length l = 12m,
Area = πr² = π* (2*10⁻⁴)² m² ≈ 3.14 * (2*10⁻⁴)² m²
R = ρl/A
≈ 3.14 * 10⁻⁸ * 12 / (3.14 * (2*10⁻⁴)²)
≈ 3
Resistance, R ≈ 3 Ω
Answer : The time required is, 16.1 minutes.
Explanation :
First we have to calculate the amount of heat required to increase the temperature is:


where,
Q = amount of heat required = ?
m = mass
= density of air = 
V = volume of air
C = specific heat of air = 
= change in temperature = 
Now put all the given values in above formula, we get:



Now we have to calculate the time required.
Formula used :

where,
t = time required = ?
Q = amount of heat required = 
P = power = 1500 W
Now put all the given values in above formula, we get:


Thus, the time required is, 16.1 minutes.
Answer:
E = 124 eV
Explanation:
Given,
The frequency of the X-rays, ν = 3.0 x 10¹⁰ Hz
The formula for calculating the energy of the electromagnetic waves of a single photon of having frequency 'ν' is given by the relation
E = hν joules
Where,
h - Planck's constant (6.626 x 10⁻³⁴ Js)
Substituting the values in the above equation
E = 6.626 x 10⁻³⁴ Js x 3.0 x 10¹⁰ Hz
= 1.9878 x 10⁻²³ J
Converting it into eV
E = 1.9878 x 10⁻²³ x 6.242 x 10¹⁸ eV
= 124 eV
Therefore, the energy in electron volts of X-rays is, E = 124 eV
100m ÷ 50s = 2m/s
Just some simple divison.