We measure emf of a cell by potentiometer and then by a voltmeter. We get values ${\mathrm{E}}_1$ and ${\mathrm{E}}_2$. Which one is bigger?

We are to find a very accurate value of a potential difference. Which type of potentiometer and driving cell should we chose?

How voltmeter and ammeter should be joined in an electric circuit?

Why voltmeter should have a very high resistance and ammeter should have a low resistance?

What are ideal cell, ideal voltmeter and ideal ammeter?