# Clock speed vs Drift speed

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1. Jun 20, 2015

### Pythagorian

I am just beginning to educate myself about electricity and computers. Every time I read something I realize my ignorance is even greater than I imagined. For instance, I was stunned to learn that the drift speed of a typical current is so slow.
• An AC circuit generates an electromagnetic field that travels at a significant fraction of the speed of light. But in a DC circuit no electromagnetic field is generated.
• A computer or cell phone operates using a DC circuit, and thus does not generate an electromagnetic field.
• Thus I am led to assume that in a computer or cell phone the speed should be limited by the slow drift speed of charges.
• But these devices process instructions at a rate of millions, if not billions per second.
So it is clear to me that I am missing some important pieces of information. Please help me to understand or it least point me in the direction that my education needs to go.

Thanks

2. Jun 20, 2015

### Staff: Mentor

There is an electromagnetic field, but it is static in a perfect DC setup (nothing changes at all).
They use both. Also, the voltage inside the active compoents switches frequently - that is the point of the computer: compute things.
Why should it?

3. Jun 20, 2015

### rootone

One thing you need to bear in mind is that the reason your cell phone works at all is because it is able to receive and transmit microwaves, (EM).

4. Jun 20, 2015

### Pythagorian

Let me try to refine my question.

What is carrying the force that is doing the switching inside a processor? Is it the movement of electrons? Or is it an electromagnetic field?

5. Jun 20, 2015

### jerromyjon

6. Jun 20, 2015

### Staff: Mentor

Both are related. Electrons move due to an electromagnetic field (mainly due to the electric part), and the electromagnetic field exists due to the charge density (and current flow) that gets influenced by the motion of charge.

7. Jun 20, 2015