State one way of increasing the strength of a electromagnet so formed

Increase the number of turns of wire on the core.

Why this works

For an electromagnet the magnetic field strength \(B\) (or magnetomotive force) is given by

\[ B \propto N I \]

where \(N\) is the total number of turns of the coil and \(I\) is the current flowing through it. By keeping the current same and adding more turns, the product \(N I\) increases, so the magnetic field becomes stronger.

Practical way to do it

1. Choose a thin enamelled copper wire (e.g., 0.5 mm diameter) so that many turns can be wound without making the coil too bulky.
2. Wrap the wire tightly and uniformly around the iron/steel core, layer by layer, ensuring each turn lies next to the previous one.
3. Secure the ends of the wire and connect them to the power source; the current remains unchanged.

Common exam mistake

Students often write “increase the current” as the only method, forgetting that the current is limited by the power source and heating. In exams, mentioning “increase the number of turns” earns full credit and is safer practically.

Thus, adding more turns to the coil is a reliable way to increase the strength of an electromagnet.