A group of students conducted an activity for science class. They used a galvanometer, which is an instrument that can detect an electric current. They followed these steps:

Question

Obtain a 100 foot long electrical extension cord.
Connect each end of the extension cord to the galvanometer.
Using duct tape, secure part of the extension cord to the ground as shown below.
Swing the top part of the extension cord as if a person were to enter to jump rope.
Have a student observe the galvanometer while the cord is rotating.

Students observed that the needle of the galvanometer moves. What does this demonstrate?
A.
Moving an electrical conductor through Earth's magnetic field induces an electric current.
B.
Moving an electrical conducting wire close to the ground changes Earth's magnetic field.
C.
Moving an electrical conducting wire through a magnetic field changes the wire's conductivity.
D.
Moving an electrical conductor next to an electric current produces a magnetic field.

Answer 1

The correct answer is:

A. Moving an electrical conductor through Earth's magnetic field induces an electric current.

This is based on Faraday's law of electromagnetic induction, which states that a change in the magnetic environment of a coil or conductor will induce an electromotive force (EMF) and hence an electric current in the conductor. In this experiment, as the extension cord (which acts as a conductor) is swung through the Earth's magnetic field, it induces a current, which is detected by the galvanometer.