(a(i))[1]
State the relationship between the current $I_B$ in the battery, the current $I_1$ in the fixed resistor and the current $I_2$ in the variable resistor.
(a(ii))[1]
State an equation linking the potential difference (p.d.) $V_B$ across the battery, the p.d. $V_1$ across the fixed resistor and the p.d. $V_2$ across the variable resistor.
(b)[2]
The battery p.d. is $9.0\,\text{V}$. The resistance of R is $500\,\Omega$. Calculate the current in R.