A galvanometer can be used to detect electrical current.
Objective: Students will:
• Make a simple galvanometer.
• Learn to use the galvanometer to measure electrical flow.
Understand energy, its transformations, and interactions with matter.
Identify forms of various types of energy and their effects on matter
FORMING THE QUESTION/HYPOTHESIS
Make observations. Ask questions or form hypotheses based on those observations, which can be explored through scientific investigations.
Part A: Insulated Bell wire, Compass, Cardboard, Brass Brads
Part B: C or D battery, Flashlight bulb with socket, Insulated Bell Wire
1. Use a 15 x 9 cm piece of cardboard. Place the compass in the center of the cardboard and trace its outline. Remove the compass and cut two “dime sized” holes in the cardboard and put brads in place as indicated.
2. Strip 2cm of insulation from the ends of a 60cm piece of bell wire. Wind the wire around the compass by passing the wire through the “dime sized” holes and then secure the wires by passing them around the brads. Attach the alligator clips to the ends of the wire.
1. Setup the galvanometer, C or D battery, and a flashlight bulb in the socket as pictured.
2. Before attaching the alligator clips to the battery, align the compass needle so that it is parallel to the coiled wire.
3. Attach the alligator clips to complete the circuit. Does the needle move? If so, why?
4. Reverse the connections at the battery terminals. How does the needle behave when the circuit is complete?
An instrument used to detect electric current is called a galvanometer. This type of instrument can be made by winding a coil of insulated bell wire around a compass to a piece of cardboard, and connecting the voltage source to the instrument.
The purpose of the loop of wire is to make the detecting instrument more sensitive to small electric currents.
The galvanometer would be aligned so that the compass needle is parallel to the looped wires. The coil of wires should be in a north-south plane.
When a current flows through the coil, a magnetic field is produced around the coil. The lines of force in the coil will tend to deflect the needle from its north-south direction. In a simple galvanometer such as this, the amount of deflection of the needle will be only a rough measure of the strength of the current.