Question

4.2.2 quiz: electromagnetism
question 6 of 10
what happens to the strength of an electromagnet when the voltage in the coils of the solenoid is decreased?
a. it decreases.
b. it depends on what metal makes up the solenoid.
c. it remains the same.
d. it increases.

Explanation:

The strength of an electromagnet is related to the current in the solenoid. According to Ohm's law \(I=\frac{V}{R}\) (where \(I\) is current, \(V\) is voltage, and \(R\) is resistance). Assuming the resistance \(R\) of the solenoid coils is constant, when the voltage \(V\) is decreased, the current \(I\) decreases. The magnetic field strength \(B\) of a solenoid is given by \(B = \mu_0nI\) (where \(\mu_0\) is the permeability of free space, \(n\) is the number of turns per unit length, and \(I\) is current). Since \(B\) is directly proportional to \(I\), a decrease in \(I\) (due to decreased \(V\)) will lead to a decrease in \(B\) (electromagnet strength).

Answer:

A. It decreases.