If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

## Physics library

### Course: Physics library>Unit 18

Lesson 5: Discovery of electromagnetism

# Battery meter (galvanometer)

Simple device which we can use to measure our homemade batteries. You can test it with any household battery first. What does this deflection represent? What forces are involved? Created by Brit Cruise.

## Want to join the conversation?

• why is the author never talking or giving explanations to the videos?
• The idea is to get you thinking about what's going on (and try it yourself leading to your own discoveries). Eventually I will add a video at the end of each tutorial with a summary
• Can this experiment harm the compass?
• It will not harm the compass unless the compass is exposed to a magnetic field for long enough that it gets remagnetised in a different direction.
• Nice! So simple too. But such a device can only detect the presence of current. How can we determine the level of current?
• for this purpose we use an instrument known as ammeter.the galvanometer is just the primitive version of the ammeter.
• When the compass spins, does that mean that the battery is good or bad?
(1 vote)
• It means the battery is good, and working. When electricity from the battery travels around the coils, it creates a magnetic field. This field is what causes the compass to spin. If the battery were dead, there would not be an electric current, so there would be no magnetic field.
• Are the alligator clips attached to the ends of the magnet wire?
• The answer would be probably yes. If , it wasn't connected , then I don't think the compass would detect the battery .
(1 vote)
• Are the alligator clips attached to the end of magnet wire?
• Yes. The compass would not be spinning if the circuit is not complete.
(1 vote)
• So does this work sorta like an electromagnet?
(1 vote)
• Good call. A voltage source, battery, attached to a coil, makes an electromagnet. putting a compass in the middle of the coil allows you to determine whether your voltage source, battery, is active/working.
• Does the amount of magnetic wire I use to circumvent the compass matter? The more wire the more accurate the galvanometer is?
(1 vote)
• Hello Colin,

Accurate may not be the correct word. With more with the galvanometer would be more sensitive. The needle would deflect with a smaller current.

Regards,

APD