Question

question 3
electromagnets
use the following information to answer the questions.
an electromagnet is a type of magnet in which the field is usually not magnetic, such as
an iron nail, can be made magnetic in order to become a magnet.
a student builds an electromagnet using a battery, a plastic rod, and wire that is insulated.
the wire is then wrapped around the rod 10 times and then connected to the battery.
what changes could the students make to increase the strength of the electromagnet?
(a)
select all that apply. there are three (3) correct answers.
a replace the wire with a wire that has less resistance
b increase the length of the wire
c replace the plastic rod with an iron nail
d wrap more loops of the wire around the nail
e remove half of the loops around the nail
f decrease the voltage of the battery
(b) when creating the electromagnet, there were several possible
variables that could be investigated. those variables included the
thickness of the wire, the number of loops made around the rod, the type
of rod, and the voltage of the battery. in order to test the strength of
all of these changes would be made in which of the electromagnet, which would not be the variable?
a the thickness of the wire
b the type of rod
c the number of loops of wire around the rod
d the voltage of the battery

Explanation:

• Option A: Using a wire with less resistance allows more current to flow (by Ohm's law \(I = \frac{V}{R}\), where \(V\) is voltage and \(R\) is resistance). More current in an electromagnet (which is based on the principle that a current - carrying wire produces a magnetic field) increases its strength.
• Option B: Increasing the length of the wire (assuming the wire is part of the coil) increases the number of turns in the coil (if we keep the radius of the coil approximately the same). The magnetic field strength of an electromagnet \(B\propto nI\) (where \(n\) is the number of turns per unit length and \(I\) is the current). More turns (for a given current) increase the magnetic field strength.
• Option C: Replacing the plastic rod (non - magnetic) with an iron nail (a ferromagnetic material) allows for magnetic domain alignment in the iron nail. Ferromagnetic materials can greatly enhance the magnetic field of an electromagnet.
• Option D: Wrapping more loops of wire around the nail increases the number of turns \(n\) in the coil. As \(B\propto nI\), more turns increase the magnetic field strength (for a fixed current).

• Option E: Removing half of the loops around the nail decreases the number of turns \(n\). Since \(B\propto nI\), this will decrease the strength of the electromagnet.
• Option F: Decreasing the voltage of the battery decreases the current \(I\) (by \(I=\frac{V}{R}\), assuming \(R\) is constant). Since \(B\propto nI\), a decrease in current will decrease the strength of the electromagnet.

Answer:

A. Replace the wire with a wire that has less resistance, B. Increase the length of the wire, C. Replace the plastic rod with an iron nail, D. Wrap more loops of wire around the nail