Physics > Current Electricity > 10.0 Electrical devices
Current Electricity
1.0 Introduction
2.0 Conduction of current in a metal
3.0 Ohm's law
3.1 Temperature dependence of resistance
3.2 Resistivities of different materials
3.3 Limitations of ohm's law
4.0 Combination of Resistors
5.0 Electromotive force $\left( \xi \right)$
6.0 Heating effect of current
7.0 Wheatstone bridge
8.0 Metre Bridge Or Slide wire bridge
9.0 Potentiometer
9.1 Comparison of emfs of two primary cells.
9.2 Determination of Internal resistance of a cell using potentiometer
10.0 Electrical devices
10.1 Ammeter
3.2 Resistivities of different materials
3.3 Limitations of ohm's law
9.2 Determination of Internal resistance of a cell using potentiometer
It is an instrument which is used to measure currents.
It connected in series with the branch in which current is to be measured.
An ideal ammeter has zero resistance.
A galvanometer with resistance $R_g$ and current rating $I_g$ can be converted into an ammeter of current rating $I$ by connecting a suitable shunt resistance $S$ in parallel to it.
Applying Kirchhoff's loop law we get, $$\begin{equation} \begin{aligned} \Rightarrow (I - {I_g})S - {I_g}G = 0 \\ \Rightarrow S =\frac{{{I_g}G}}{{(I - {I_g})}} \\\end{aligned} \end{equation} $$
Current rating
Current rating is defined as the current carrying capacity.
