A-level Physics (Advancing Physics)/Charge

Electrons, like many other particles, have a charge. While some particles have a positive charge, electrons have a negative charge. The charge on an electron is equal to approximately -1.6 x 10⁻¹⁹ coulomb. The coulomb (commonly abbreviated C) is the SI unit of charge. One coulomb is defined as the electric charge carried by 1 ampere (amp) of current in 1 second. It is normal to ignore the negative nature of this charge when considering electricity.

If we have n particles with the same charge Q_particle, then the total charge Q_total is given by:

Q_total = n Q_particle

By a simple rearrangement:

$n={\frac {Q_{total}}{Q_{particle}}}$

Questions

1. How much charge do 1234 electrons carry?

2. How many electrons does it take to carry 5 C of charge?

3. The total charge on 1 mole of electrons (6 x 10²³ particles) is equal to 1 Faraday of charge. How many coulombs of charge are equal to 1 Faraday?

4. The mass of a ball is 50 mg. It is supplied 5 C of charge. Will there be any change in the mass of the ball? If so, calculate the change of the mass.

Worked Solutions