1. Aug 7, 2009

### user111_23

*subject edited*

Is electrical energy in the form of EM waves? If so, how does it do work on a device?

Last edited: Aug 8, 2009
2. Aug 8, 2009

### Staff: Mentor

A changing magnetic field produces an electric field, according to one of Maxwell's equations.

3. Aug 8, 2009

### user111_23

Just curious: are my questions too confusing? If they are, I can simplify them.

4. Aug 8, 2009

### Staff: Mentor

Maybe pick just the single most important question and avoid the rapid-fire barrage. Many people on this forum could answer any one of those questions, but all of them together is just tiring.

5. Aug 8, 2009

### user111_23

Usually I try to cram many different questions into a single topic. I guess that's a bad idea. :tongue:

6. Aug 9, 2009

### Born2bwire

Electromagnetic waves do contain and propagate energy. However, their main purpose in an electrical circuit is to simply propagate a signal. Most circuit devices work via the use of charges. The electromagnetic wave moves the charges throughout the transmission lines (wires) of a circuit. When these waves meet a device, the charges, currents, and voltages that the wave sets up at the devices is what makes the device work. For example, with a transistor, the electromagnetic wave will create voltages across the gate and drain of the transistor (MOSFET in this case) with respect to the source. These voltages will create fields within the MOSFET and cause the movement of charges creating currents.

I am not sure if you want to quantify the electrical energy of a circuit as being in the form of electromagnetic waves. The waves are energy and they propagate the energy, but what is more relevant is how you measure and interact with the energy as the amount of energy your circuit can get out of these waves can vary.

7. Aug 9, 2009

Staff Emeritus
What's confusing is to change your question in mid-thread by erasing the old one and posting the new one. Now nobody can tell what were the questions that went with the answers.

8. Aug 9, 2009

### Staff: Mentor

Electrical energy is in the form of EM fields. All EM waves are fields, but not all EM fields are waves. See: http://hyperphysics.phy-astr.gsu.edu/HBASE/electric/engfie.html#c1

The fields do work because they exert a force (f=q(vxB+E)) on a charge and w=f.d