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| 184_notes:q_enc [2018/05/15 17:00] – curdemma | 184_notes:q_enc [2018/07/24 15:17] – [Charge Density and Charge] curdemma |
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| {{youtube>YhTl8JmBQ6E?large}} | {{youtube>YhTl8JmBQ6E?large}} |
| ==== Charge Density and Charge ==== | ==== Charge Density and Charge ==== |
| [[184_notes:dq|Before we talked about charge density]] in terms of finding a dQ, where we //__assumed a uniform (or constant) charge density__//. We will make that same assumption again here (the more complicated non-uniform charge densities may be covered in upper division courses). For a uniform charge distribution, the charge density tells you how much charge there is per unit length (for 1D lines of charge), per area (for 2D sheets of charge), or per volume (for 3D shapes of charge). For 1D charge distributions, we use $\lambda$ as the charge density (which has units of $C/m$); for 2D charge distributions, we use $\sigma$ as the charge distribution (which has units of $C/m^2$); and for 3D charge distributions, we use $\rho$ as the charge density (which has units of $C/m^3$). | [[184_notes:dq|We have talked about charge density]] in terms of finding a $dQ$, where we //__assumed a uniform (or constant) charge density__//. We will make that same assumption again here (the more complicated non-uniform charge densities may be covered in upper division courses). For a uniform charge distribution, the charge density tells you how much charge there is per unit length (for 1D lines of charge), per area (for 2D sheets of charge), or per volume (for 3D shapes of charge). For 1D charge distributions, we use $\lambda$ as the charge density (which has units of $C/m$); for 2D charge distributions, we use $\sigma$ as the charge distribution (which has units of $C/m^2$); and for 3D charge distributions, we use $\rho$ as the charge density (which has units of $C/m^3$). |
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| If we know the total charge and the total length/area/volume, we can calculate the charge density using: | If we know the total charge and the total length/area/volume, we can calculate the charge density using: |