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The velocity that electricity propagates is related to the dielectric in the cable. For EM waves in free space, the speed is that of light but there is only the base dielectric of free space: -

So as the permittivity (\$\epsilon\$) increases so velocity reduces.

The characterisitic impedance of free space is also related to those terms: -

Basically, if you compared both equations, as characteristic impedance drops (due to permittivity increasing), velocity of propagation also drops.

The product of speed and impedance is \$\dfrac{1}{\epsilon}\$

And the ratio of impedance to speed is \$\mu_0\$.

I've used \$\mu_0\$ above (rather than \$\mu\$) because there is no significant increase in magnetic permeability due to a cable's construction.

The velocity that electricity propagates at is related to the dielectric in the cable. In free-space, an EM wave travels at the speed of light but there is only the permittivity of free space (\$\epsilon_0\$)to hinder it: -

So, as the permittivity (\$\epsilon_r\$) rises, velocity decreases. Magnetic permeability is the other factor but this barely changes between a cable and free-space.

The characterisitic impedance of free space is also related to those terms: -

Basically, if you compared both equations, as characteristic impedance drops (due to permittivity increasing), velocity of propagation also drops.

The product of speed and impedance is \$\dfrac{1}{\epsilon}\$

And the ratio of impedance to speed is \$\mu_0\$.

I've used \$\mu_0\$ above (rather than \$\mu\$) because there is no significant increase in magnetic permeability due to a cable's construction.

The velocity that electricity propagates is related to the dielectric in the cable. For EM waves in free space, the speed is that of light but there is only the base dielectric of free space: -

So as the permittivity (\$\epsilon\$) increases so velocity reduces.

The characterisitic impedance of free space is also related to those terms: -

Basically, if you compared both equations, as characteristic impedance drops (due to permittivity increasing), velocity of propagation also drops.

The product of speed and impedance is therefore \$\dfrac{1}{\epsilon}\$

The velocity that electricity propagates is related to the dielectric in the cable. For EM waves in free space, the speed is that of light but there is only the base dielectric of free space: -

So as the permittivity (\$\epsilon\$) increases so velocity reduces.

The characterisitic impedance of free space is also related to those terms: -

Basically, if you compared both equations, as characteristic impedance drops (due to permittivity increasing), velocity of propagation also drops.

The product of speed and impedance is \$\dfrac{1}{\epsilon}\$

And the ratio of impedance to speed is \$\mu_0\$.

I've used \$\mu_0\$ above (rather than \$\mu\$) because there is no significant increase in magnetic permeability due to a cable's construction.

The velocity that electricity propagates is related to the dielectric in the cable. For EM waves in free space, the speed is that of light but there is only the base dielectric of free space: -

So as the permittivity (\$\epsilon\$) increases so velocity reduces.

The characterisitic impedance of free space is also related to those terms: -

Basically, if you compared both equations, as characteristic impedance drops (due to permittivity increasing), velocity of propagation also drops.

The ratio of speed to impedance is therefore \$\epsilon\$

The velocity that electricity propagates is related to the dielectric in the cable. For EM waves in free space, the speed is that of light but there is only the base dielectric of free space: -

So as the permittivity (\$\epsilon\$) increases so velocity reduces.

The characterisitic impedance of free space is also related to those terms: -

Basically, if you compared both equations, as characteristic impedance drops (due to permittivity increasing), velocity of propagation also drops.

The product of speed and impedance is therefore \$\dfrac{1}{\epsilon}\$