Give the direction of the conventional current when the circuit is closed. State one function each of RH, Q, X, z.

(a) The direction of the conventional current when the circuit is closed is from the positive terminal of the battery, through the fixed resistor $R$, towards the capacitor.

(b) Magnitude of the conventional current when the circuit is closed (initial current).

Step 1: Formula for initial charging current in RC circuit.

$I_0 = \frac{V}{R}$

where $V$ is the battery emf and $R$ is the fixed resistor.

Step 2: Substitute values (from diagram: $V = 6\,\mathrm{V}$, $R = 3\,k\Omega = 3000\,\Omega$).

$I_0 = \frac{6}{3000}$

Step 3: Simplify.

$I_0 = 0.002\,A = 2\,mA$

2 mA

(c) State the function of each of:

Fixed resistor $R$: Limits the maximum current to prevent damage to the circuit and provides the time constant with the capacitor.

Capacitor $C$: Stores electrical charge/energy.

Battery: Supplies the emf to charge the capacitor.

Switch: Allows the circuit to be completed or opened.

(d)(i) $R_x$ (the fixed resistor value).

$R_x = 3\,\mathrm{k\Omega}$

(ii) Capacitance $C$ (assume typical or from time constant).

Assume time constant $\tau = 6\,\mathrm{s}$ from graph, $\tau = RC$.

Step 1: Formula.

$\tau = R C$

Step 2: Substitute $R = 3000\,\Omega$, $\tau = 6\,\mathrm{s}$.

$C = \frac{\tau}{R} = \frac{6}{3000} = 0.002\,F = 2\,mF$

2 mF

(iii) Perhaps time constant.

$\tau = RC = 3000 \times 0.002 = 6\,s$

6,\mathrm{s}