The strength of the magnetic field generated by a solenoid (or coils of wire) is influenced by both the material the core is made from and the number of coils.
In this case:
- An iron nail acts as a ferromagnetic core, which enhances the magnetic field created by the coils of wire significantly compared to non-magnetic materials.
- The number of coils also plays a crucial role: more coils produce a stronger magnetic field.
Now, let's evaluate the options:
a. An iron nail with 7 coils of copper wire wrapped around it.
b. A plastic nail with 7 coils of copper wire wrapped around it.
c. A plastic nail with 17 coils of copper wire wrapped around it.
d. An iron nail with 17 coils of copper wire wrapped around it.
From these options, the two with iron nails (a and d) will produce a stronger magnetic field than those with plastic nails. Between option a (with 7 coils) and option d (with 17 coils), option d will produce a stronger magnetic field due to the greater number of coils.
Thus, the option that would have the strongest magnetic field is:
d. An iron nail with 17 coils of copper wire wrapped around it.