the number of electrons in a copper penny is approximately 10*10^23. How large would the force be on an object if it carried this charge and were repelled by an equal charge one meter away?


I am using don't panic volume 2. How do you do this problem step by step?

Verified Answer :

The charge on the electron is 1.6x10^-19C. So, 10^24 of them will be a  charge of 1.6x10^5C, F = q1xq2/[(4pi epsilon nought)r^2]

Answer:

The force of repulsion between charges will be 2.309 N.

Explanation:

The number of electrons in a copper penny =N = \(10\times 10^{23}\)

Charge on an electron = \(e=-1.602\times 10^{-19} C\)

Total charge of the N electrons = Q

\(Q=N\times e\)

\(Q=10\times 10^{23}\times 1.602\times 10^{-19}C=-1.602\times 10^{-5}C\)

The force be on an object if it carried this charge and were repelled by an equal charge one meter away.

\(Q=-1.602\times 10^{-5}C\)

\(q=Q\)

Let the force of repulsion be F.

Distance between the Q and q charges = r =1 m

\(F=k\frac{Qq}{r^2}\) (Coulomb law)

\(F=9\times 10^9 Nm^2/C^2\times \frac{(-1.602\times 10^{-5} C)\times (-1.602\times 10^{-5} C)}{(1m)^2}\)

\(F=2.309 N\)

The force of repulsion between charges will be 2.309 N.