Copyright © University of Cambridge. All rights reserved.

## 'Battery Modelling' printed from http://nrich.maths.org/

A battery is modelled as a $24\mathrm{V}$ EMF in series with an internal resistance of $2\Omega$. The battery is being charged by a constant current source as shown in the network below. The ammeter, used to measure the current through the battery, has a voltage drop of $2\mathrm{V}$ at full range scales. Here it is set to a $20\mathrm{A}$ range and reads a current of $2\mathrm{A}$.

What is the value of the constant current supplied?

What fraction of the input power is supplied to the battery?

What current would flow into the battery if we now replaced the ammeter with a wire of zero impedance?