# Magnetism from Electricity

## Key Questions

• An electric field could.

In theory the gravitational and electric fields could accelerate a moving electron but practically speaking for most cases only an electric field will accelerate the electron noticeably. The magnitudes of the electric and gravitational forces are a product of the charge and mass respectively with some other values.

The charge on an electron is $- 1.6 . {10}^{-} 19 C$ and the (rest) mass of an electron is $9.1 . {10}^{-} 31 k g$. As you can see the charge is several orders of magnitude larger than the mass. That fact combined with the constants of each equation mean that for most cases only an electric field will exert a large enough force on an electron to cause it to speed up (or slow down).

Electric force - Coulomb's Law:
F_e=1/(4πε_0)(q_1q_2)/r^2

Gravitational force - Newton's Law of Gravitation:
${F}_{g} = G \frac{{m}_{1} {m}_{2}}{r} ^ 2$

The magnetic force will not change the speed of a moving electron because the magnetic force is always perpendicular to the velocity. A moving electron in a uniform magnetic field will undergo uniform circular motion.

• In a classic electric bell (not the modern day electronic ones), an electromagnet was fitted such that when the switch was turned on, it created a magnetic field due to which a nearby magnetic hammer would be attracted to it and strike it thereby creating the sound of the bell. When the switch is turned off, the hammer goes back to it's original position due to springs fitted.

• Electromagnetism is the phenomenon of generation of magnetic fields from electric currents.

The magnitude of fields produced depends on the current, orientation of the wire, distance of the wire from which the field is measured, length of the wire element. These are studied under electromagnetism.