(a) (i)
For the correct answer:
(soft) iron
An electromagnet requires a core that can be easily magnetized and demagnetized (a temporary magnetic material). Soft iron is the standard material used for this purpose because it loses its induced magnetism almost instantly when the electrical current is switched off.
(a) (ii)
For the correct answer:
$8$ (cells)
The total electromotive force (e.m.f.) of cells connected in series is equal to the sum of their individual e.m.f. values. To find the total number of cells, you divide the total battery e.m.f. ($12$ V) by the e.m.f. of a single cell ($1.5$ V). Using the calculation $12 \div 1.5 = 8$, we find that there are $8$ cells in the circuit.
(b) (i)
For the correct answer:
(plotting) compass
A plotting compass contains a small magnetic dipole that aligns itself with the local magnetic field. By placing it at various positions around the electromagnet, the north pole of the compass needle will point in the direction of the magnetic field lines, allowing the field pattern to be visualized.
(b) (ii)
For the correct answer:
North OR N (pole)
The polarity of an electromagnet can be determined using the right-hand grip rule. If you wrap the fingers of your right hand around the solenoid in the direction of the current (which points downwards on the visible front coils), your thumb points to the right. Therefore, the right end (labelled X) is the North pole.
(c)
For the correct calculated value:
$9.6$ V
The potential difference across a component can be calculated using the resistance equation, which can be rearranged to $V = I \times R$. Given the current $I = 1.2$ A and the resistance $R = 8.0$ Ω, you substitute these values into the formula to get $V = 1.2 \times 8.0$. This yields a potential difference of $9.6$ V.
