Disclaimer: Due to unforeseen difficulties, we have had to take down the images on this notes page. They will be replaced shortly. We apologise for the inconvenience, but hope that the new images will provide you with an even better learning experience.


    1. Describe an experiment that shows that a changing magnetic field can induce an e.m.f. in a circuit

A generator contains coils of wire that spin in a magnetic field. A potential difference (p.d.) is created or induced in the wire when it cuts across the magnetic field lines. We refer to this source of pd as induced electromotive force* (e.m.f.) or an induced voltage. Emf is measured in volts (V).

*when charge flows through a cell it is given energy by the cell.  The number of joules of energy given to each coulomb of charge that passes through the cell is the e.m.f. of the cell

Wrap a wire around a metal. Then connect the wire to a voltmeter or galvanometer (devices used to measure voltage/pd). If you move the metal up and down between the opposite poles of two magnets, you can see the voltage changing, indicating that e.m.f. has been induced in the wire, or that an electrical current has been produced.

The production of an e.m.f. by moving a wire in a magnetic field is known as electromagnetic induction.


    1. State the factors affecting the magnitude of an induced e.m.f
      • The rate/speed in which the wire moves: the faster the movement, the higher the e.m.f.
      • The strength of the magnet: the stronger the magnets, the more the e.m.f. produced
      • The number of coils the wire makes: when the wire is coiled around several times, the no. of magnetic fields intersecting increases, and the current/voltage produced also increases.




Notes submitted by Lintha

Click here to go to the next topic.

Click here to go back to the previous topic.

Click here to go back to the Science menu.


What Do You Think?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.