$A$ hot plate of an electric oven connected to a $220\, V$ line has two resistance coils $A$ and $B$,each of $24\,\Omega$ resistance,which may be used separately,in series,or in parallel. What are the currents in the three cases?

(N/A) Supply voltage,$V = 220\, V$.
Resistance of each coil,$R = 24\,\Omega$.
$(i)$ When coils are used separately:
According to Ohm's law,$I = V / R$.
$I_1 = 220 / 24 = 9.17\, A$.
$(ii)$ When coils are connected in series:
Total resistance,$R_s = R + R = 24 + 24 = 48\,\Omega$.
$I_2 = V / R_s = 220 / 48 = 4.58\, A$.
$(iii)$ When coils are connected in parallel:
Total resistance,$1 / R_p = 1 / R + 1 / R = 1 / 24 + 1 / 24 = 2 / 24 = 1 / 12$.
So,$R_p = 12\,\Omega$.
$I_3 = V / R_p = 220 / 12 = 18.33\, A$.