Question

alice builds an electric motor by positioning an electromagnet between the poles of a permanent magnet. when the electromagnet turns, the current through it switches direction because its connections to the voltage source are reversed. the repeated switching of the electromagnets poles causes it to spin. this particular motor is used to turn the wheels of a toy car. which of the following actions would increase the amount of force applied to the wheels of the toy car? a. decreasing the number of loops in the electromagnets coil b. increasing the distance between the magnets poles and the electromagnet c. decreasing the electric current running through the electromagnet d. replacing the magnet with a stronger magnet

Explanation:

Step1: Analyze each option

• Option A: Decreasing the number of loops in the electromagnet's coil reduces the magnetic field strength of the electromagnet. According to the formula for the force on a current - carrying conductor in a magnetic field \(F = BIL\sin\theta\) (where \(B\) is the magnetic field strength, \(I\) is the current, \(L\) is the length of the conductor in the magnetic field, and \(\theta\) is the angle between the current and the magnetic field), a weaker magnetic field (due to fewer loops) will result in a smaller force.
• Option B: Increasing the distance between the magnet's poles and the electromagnet weakens the magnetic field \(B\) at the location of the electromagnet. Using the formula \(F = BIL\sin\theta\), a weaker \(B\) leads to a smaller force.
• Option C: Decreasing the electric current \(I\) running through the electromagnet. From the formula \(F = BIL\sin\theta\), a smaller \(I\) will cause a smaller force.
• Option D: Replacing the magnet with a stronger magnet increases the magnetic field strength \(B\). Using the formula \(F = BIL\sin\theta\), a larger \(B\) will result in a larger force.

Answer:

D. replacing the magnet with a stronger magnet