Question

A series of four different electromagnets are each held over a pile of paper clips. Each electromagnet is the same size and is held at the same distance above the paper clips. If each circuit diagram below represents one of the electromagnets tested, which electromagnet most likely attracted the most paper clips?


W.
X.

Y.
Z.
A.
Z
B.
X
C.
W
D.
Y

Answer 1

I don't see the circuit diagrams — could you either upload the image or describe each circuit (number of battery cells, whether the switch is closed, presence of resistors, number of coil turns, etc.)?

If you want to pick the strongest electromagnet yourself, use these rules:
- Strength ∝ number of turns in the coil × current through the coil.
- Current is larger with a higher net voltage (more batteries in series) and smaller with added resistance or batteries opposing each other.
- A closed switch is required; an open switch gives no magnetism.
- An iron core inside the coil greatly increases strength.
So the diagram with the most coil turns, the highest effective battery voltage (no opposing cells), a closed circuit, no extra resistance, and an iron core will attract the most paper clips.