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3 years ago

I don't understand when to use the formule with the constant k, and when to use the formula without it.

Physics

1 answer:

White raven [17]3 years ago

3 0

Answer:

This appears to be the formula for the electrical force between 2 objects.

You need this constant to calculate the electrical force between 2 charged objects.

Note that k = (1 / 4 * π ∈0)

∈0 is called the permittivity constant and ∈0 = 8.85E-12 farad/m

k = ( 1 / (4 * 3.28 * 8.85E-12) = 8.99E9

This makes F reasonably easy to remember as

F = 9E9 Q1 * Q2 / R^2 Newtons for the electrical force between Q! and Q2 separated by R

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Dima020 [189]

Explanation:

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3 years ago

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marshall27 [118]

Answer:

$P(3600)=593.247W$

Explanation:

First, let's find the voltage through the resistor using ohm's law:

$V=IR=20*8=160V$

AC power as function of time can be calculated as:

$P(t)= V*I*cos(\phi)-V*I*cos(2 \omega t-\phi)$ (1)

Where:

$\phi=Phase\hspace{3}angle\\\omega= Angular\hspace{3}frequency$

Because of the problem doesn't give us additional information, let's assume:

$\phi=0\\\omega=2 \pi f=2*\pi *(60)=120\pi$

Evaluating the equation (1) in t=3600 (Because 1h equal to 3600s):

$P(3600)=160*8*cos(0)-160*8*cos(2*120\pi*3600-0)\\P(3600)=1280-1280*cos(2714336.053)\\P(3600)=1280-1280*0.5365255751\\P(3600)=1280-686.7527361=593.2472639\approx=593.247W$

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