Have you ever wondered how vending machines check the values of coins you place into their coin slots? A vending machine detects the amount of voltage produced while the coin moves through a magnetic field. An electric current is produced in the metal coin when the conductor cuts the lines of force of the magnetic field inside the vending machine. The size of the coin is determined by the amount of voltage detected by the vending machine.

If, for example, the conductor is a coil of wire instead of a coin, a voltage may be generated in the wire by moving a magnet through the coil. In this activity, you will make coils of different sizes and measure the amount of voltage produced in the different numbers of coils as a magnet is moved through them. In your group, predict how increasing the number of wraps of a coil will change the amount of voltage produced. Write down your ideas about what might explain your prediction.