Explain, using energy ideas and without doing any calculation, why the potential difference across the lamp has to be smaller than the e.m.f. of the battery.
Calculate the current in the circuit.
Calculate the potential difference across the lamp.
Calculate the internal resistance of the battery.
A student is given three resistors with resistances $90\,\Omega$, $45\,\Omega$ and $20\,\Omega$. Sketch a circuit diagram to show how two of these three resistors can be connected so that the combined resistance between the terminals shown is $30\,\Omega$. Label the resistance values on your diagram.
A potential divider circuit is formed by connecting the three resistors to a battery with e.m.f. $9.0\,\text{V}$ and negligible internal resistance. The potential divider circuit gives an output potential difference $V_{\text{OUT}}$ of $3.6\,\text{V}$. The circuit diagram is shown in Fig. 6.2. On Fig. 6.2, label the resistances of all three resistors and the potential difference $V_{\text{OUT}}$.