# The simplest formula for conduction current,displacement current and loss tangent

1. Feb 27, 2005

### veinn

Apparently my lecturer has given me this type of quest and i really have no idea how to do this quest..anyone know the formula for conduction current..displacement current and loss tangent..plz give me brief idea how to do it...what i know is that for displacement current i have to differentiation..but how??plzzz help meeee

A parallel plate capacitor consists of two metal plates, of area 2 cm2, separated by 3 µm of porcelain with єr =5.7 and =2 X 10-13 Sm-1. The capacitor is connected to a 12 volt 50 Hz supply. Determine the conduction current, and compare it to the displacement current. In addition, calculate the loss tangent at frequencies of 50 Hz, 1 MHz, and 100 MHz

2. Feb 27, 2005

### marlon

The conduction current is $$I =C * \frac {dV}{dt}$$

You know how V varies with respect to t. You will need to find C, which is not that difficult.

The displacement current D can be calculated from

$$\frac{\partial D}{\partial t} = - \frac{\epsilon}{w} * \frac{dV}{dt}$$
w is the distance between the condensatorplates. Keep in mind that there is porcelain between the plates.

I am not too sure what you mean by loss tangent, but i think this is a language problem :) ???

marlon

ps : this is just a general overview to get you started on this one. I am not allowed to give too much info for the obvious reason