What is the reading of voltmeter (in volts) in the following figure?

$\text{ Resistance between }A\text{ and }B=\frac{1000\times 500}{\left(1500\right)}=\frac{1000}{3}\Omega$

So, equivalent resistance of the circuit

$R_{\mathrm{eq}}=500+\frac{1000}{3}=\frac{2500}{3}\Omega$

$\therefore$Current drawn from the cell

$i=\frac{10}{(2500/3)}=\frac{3}{250}\mathrm{A}$

Reading of voltmeter i.e. potential difference across

$AB=\frac{3}{250}\times \frac{1000}{3}=4\mathrm{V}$