To make a potentiometer, a driver cell of e.m.f. $4.0 \mathrm{V}$ is connected across a $1.00 \mathrm{m}$ length of resistance wire.

(a) What is the potential difference across each $1 \mathrm{cm}$ length of the wire? What length of wire has a p.d. of $1.0 \mathrm{V}$ across it?

To make a potentiometer, a driver cell of e.m.f. $4.0 \mathrm{V}$ is connected across a $1.00 \mathrm{m}$ length of resistance wire.

(b) A cell of unknown e.m.f. $\mathrm{E}$ is connected to the potentiometer and the balance point is found at a distance of $37.0 \mathrm{cm}$ from the end of the wire to which the galvanometer is connected. Estimate the value of $\mathrm{E}$. Explain why this can only be an estimate.

To make a potentiometer, a driver cell of e.m.f. $4.0 \mathrm{V}$ is connected across a $1.00 \mathrm{m}$ length of resistance wire.

(c) A standard cell of e.m.f. $1.230 \mathrm{V}$ gives a balance length of $31.2 \mathrm{cm}.$ Use this value to obtain a more accurate value for $\mathrm{E}$.

A resistor of resistance $6.0\Omega$ and a second resistor of resistance $3.0\Omega$ are connected in parallel across a battery of e.m.f. $4.5 \mathrm{V}$ and internal resistance $0.50\Omega$. What is the current in the battery?

(A) $0.47 \mathrm{A}$

(B) $1.8 \mathrm{A}$

(C) $3.0 \mathrm{A}$

(D) $11 \mathrm{A}$

This diagram shows a potential divider.

What happens when the temperature decreases?

(A) The resistance of the thermistor decreases and $V_{\text{out }}$ decreases.

(B) The resistance of the thermistor decreases and $V_{\text{out }}$ increases.

(C) The resistance of the thermistor increases and $V_{\text{out }}$ decreases.

(D) The resistance of the thermistor increases and $V_{\text{out }}$ increases.

A single cell of e.m.f. $1.5 \mathrm{V}$ is connected across a $0.30 \Omega$ resistor. The current in the circuit is $2.5 \mathrm{A}$.

Calculate the terminal p.d. and explain why it is not equal to the e.m.f. of the cell.

A single cell of e.m.f. $1.5 \mathrm{V}$ is connected across a $0.30 \Omega$ resistor. The current in the circuit is $2.5 \mathrm{A}$.

(b) Show that the internal resistance $r$ of the cell is $0.30\Omega$.

A single cell of e.m.f. $1.5 \mathrm{V}$ is connected across a $0.30 \Omega$ resistor. The current in the circuit is $2.5 \mathrm{A}$.

(c) It is suggested that the power dissipated in the external resistor is a maximum when its resistance $\mathrm{R}$ is equal to the internal resistance $\mathrm{r}$ of the cell.

(i) Calculate the power dissipated when $\mathrm{R}=\mathrm{r}$.

A single cell of e.m.f. $1.5 \mathrm{V}$ is connected across a $0.30 \Omega$ resistor. The current in the circuit is $2.5 \mathrm{A}$.

(c) It is suggested that the power dissipated in the external resistor is a maximum when its resistance $\mathrm{R}$ is equal to the internal resistance $\mathrm{r}$ of the cell.

(ii) Show that the power dissipated when $\mathrm{R}=0.50\mathrm{\Omega }$ and $\mathrm{R}=0.20\mathrm{\Omega }$ is less than that dissipated when $\mathrm{R}=\mathrm{r}$, as the statement suggests.